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Tuesday, 20 October 2020

Day 218 of self-isolation - The Welsh dyke

The Welsh dyke

From Friday 23rd October until 9th November, Wales is going into a stay-at-home lockdown. It's pretty much the same lockdown that we all did last March and April. Pubs and restaurants will close, but nurseries will stay open, primary schools will reopen after half-term, and in secondary schools, years 7 and 8 will return.

A lot of people are saying that the rest of the country should do the same thing - there isn't any kind of wall between Wales an England. Offa's Dyke is no longer a barrier. 

The UK is still running around 20k new cases per day, which is very high, and pressure is building up on the hospital system.




Monday, 19 October 2020

Day 217 of self-isolation - Data protection

Data protection

If you want to stop people from installing the tracking app and from taking a test, what do you think would be the best way to persuade people to avoid getting tested and not install the app?

Simple.

Tell them that the police will have access to this data.

So, obviously no sane government would ... what? They did? You're kidding.

Yes. They did.

It's almost as good as allowing Special Advisors and MPs to be exempt from the rules that the rest of us follow.

So how would someone avoid this police surveillance? Simple - they would avoid being tested, and avoid installing the app.

The rules on self-isolation are good. The tracing would be a good idea if only is worked. But discouraging people by opening this channel to the police, is a seriously dumb idea. 

I've install the app on my iPhone 7 (my iPhone 6 couldn't handle it). But will I keep it? I don't know. Sixteen million people have installed the app, which is only 25% of the population, and we need more than 60%. But will people who haven't installed it so far, get it?

Now hear this. The app isn't going to give information to the police, but the tracing service can. It's a fine distinction. The app tells you that you've been  in contact with an infected person, so you go get tested (or else you don't) and at that point, you're on the radar.

It's just another bungle.





Sunday, 18 October 2020

Day 216 of self-isolation - Manchester

Manchester

Manchester is currently at level 2. Boris wants them to be at level 3. The mayor, Andy Burnham is threatening legal action of that's imposed on the area. But the real problem wouldn't be the legal action, it would be if Mancunians refuse to comply - how will they force this? The police will follow the law, obviously, but if they are faced with mass disobedience, then what?

It's become a big row. And the rest of the country, currently at level 2, is watching, because what happens there, could happen elsewhere. 

Daily UK deaths are up to 150, a level not seen since last June, with new cases at 16,171 and there is increasing pressure to have the "circuit breaker".    

 

Saturday, 17 October 2020

Day 215 of self-isolation - Manchester is revolting

Manchester is revolting

Andy Burnham is the mayor of Manchester, and he rejects the government's decision  to put Manchester into "very high" lockdown status. He's demanding that 80% of wages be paid for closed businesses.

Can he do that?

Probably not, in law. But the lockdown relies on the cooperation of citizens. There aren't enough jails in the whole country to lock up all the people who might refuse.

Right now, about half the country is rated as high or very high. And I can't help feeling that there are two causes.

The first cause was the "Eat out to help out" scheme, which encouraged people to go back to restaurants, where you HAVE to take your mask off to eat. And the second cause has been the scheme whereby teenagers are crammed together into buildings - also known as "student hostels". Maybe that first idea wasn't as good as they thought, and result of the second action was rather inevitable.

 Burnham is also asking for the "circuit breaker" lockdown; I already explained why I don't think that will do as much as some people hope.




Friday, 16 October 2020

Day 214 of self-isolation - London is high risk

London is high risk

It's just as well we got our visit done last week, because London is now high risk. You must not meet socially with friends and family indoors in any setting unless you live with them or have formed a support bubble with them. This includes private homes, and any other indoor venues such as pubs and restaurants.

We can meet outdoors, in a group of 6 or less (including children). But it isn't summer now, and if it rains, it's going to be pretty miserable. And it'll get colder as winter draws on.

But just look at the numbers. 138 new deaths, and 18980 new infections Thursday; a similar number the day before with 137 new deaths and 19722 new infections. 

We're not in London; our area is still "medium risk", but I think that's only a matter of time.

So, we hunker down.

I've been taking 2000 IU of vitamin D each day. I'm going to start taking 15mg of zinc supplements. They cost £1.50 for 60 from Waitrose, and they're one of the things they gave Trump. I did a bit of research, and being low on zinc does make it worse. I don't know if I am low on zinc, but for 2.5p per day, it seems like a sensible precaution. The recommended dose is 11mg/day, so 15 is about right.




Thursday, 15 October 2020

Day 213 of self-isolation - the third wave

The third wave

UK is in the second wave, and it's looking worse and worse. 137 deaths today, and 19,724 new cases. That means that new cases are still growing at a horribly fast rate, and are now FOUR times as many as they were in April. Remember April? How it felt like the apocalypse?


 

Of course, now the NHS is much better at treating the virus than they were when it hit them out of the blue last March. We learned. We have treatments that we know can help. But still - there will be fatalities. And if the hospitals are swamped, the percentage of fatalities will soar. Remember "protect the NHS"?


But Iran is in the third wave. Yes, there can be a third wave.


Right now, in the UK we're trying to control the second wave, and so far, no success, as you can see from the graph. Perhaps success will come? Maybe. 

Keir Starmer is suggesting a "circuit breaker", a period of two weeks in which we all lock down 100%, as suggested by SAGE. Would this help?

In theory, yes. If everyone stays away from everyone else, the number of cases plummets dramatically. But that won't happen. First of all, there are all the "critical workers", like Bob who drives the Ocado van, and Yusuf who drives the Waitrose van. And the transport workers, and the NHS workers, and so on and so on.

But there are also the "covidiots" who think that the rules don't apply to them, like Dominic  Cummings and  Margaret Ferrier. They have undermined confidence in the government more than they realise. So how many people will follow the example of Cummings and Ferrier? Rather too many, I think.

The "circuit breaker" in an electrical circuit, stops all electricity from flowing. The Covid
"circuit breaker" is only going to be partial. Will it be enough? No. Because when the
"circuit breaker" is switched off again, we're back to where we are now.

What we need is the vaccine.

Wednesday, 14 October 2020

Day 212 of self-isolation - Computer repair

Computer repair

One of my servers has been rebooting, about once per month. This is annoying, but not devastating. However, I decided to have a look at it.

When a computer acts like this, these are the likely causes, in order of likelihood

1. Fan

2. Memory

3. Power supply

4. Motherboard

5. CPU

 

Fans are mechanical, and wear out . It's easy to spot when a fan isn't working, because the fan isn't working. In this case, all the fans were working.

Memory gives up after several years. I don't know the exact cause, but I suspect cosmic rays. I have a memory test program - in this case, it passed the test .

Power supplies have a lot of electronic components. The fans can wear out (which is obvious) or a capacitor can weaken. I have a PSU tester; when I plugged it in, it beeped many times and told me that the 3.3 volt supply was all over the place. So I think that was the problem. I replaced the PSU, and put the computer back on the rack.

Motherboards fail with the capacitors. CPUs hardly ever fail. The only way I know of testing a motherboard or CPU is to replace it. I bought a whole bunch of motherboards, CPUs and memory on eBay for £20 each, and they will last me quite a long time.

 

 




Tuesday, 13 October 2020

Day 211 of self-isolation - Medium, high or very high

Medium, high or very high risk.

It's a three tier system, which isn't going to work; more tiers are needed. And how do I find out what tier I'm in?

It's a good idea (I would say that, wouldn't I?) but they didn't quite get it right. Maybe they can make it work, but given all the past bungles, I'm not terribly optimistic.

The reason why it's a good idea, is that it makes it possible to write an unambiguous set of rules, that (hopefully) anyone can understand, and so the rules don't change, only the alert level of the area that you're in.

 You can find out which level you are at here. I would have preferred it if I could give my postcode, and it would tell me my level. I'm in Buckinghamshire, so I'm medium.

And here's what you can and cannot do at each level.


  • you must not socialise in groups larger than 6, indoors or outdoors (other than where a legal exemption applies)
  • businesses and venues can continue to operate, in a COVID-secure manner, other than those that remain closed in law
  • certain businesses are required to ensure customers only consume food and drink while seated, and must close between 10pm and 5am
  • businesses and venues selling food for consumption off the premises can continue to do so after 10pm as long as this is through delivery service, click-and-collect or drive-through
  • schools and universities remain open
  • places of worship remain open, subject to the rule of 6
  • weddings and funerals can go ahead with restrictions on numbers of attendees
  • exercise classes and organised sport can continue to take place outdoors, or indoors if the rule of 6 is followed

You should continue to:

  • follow social distancing rules
  • work from home where you can effectively do so
  • when travelling, plan ahead or avoid busy times and routes. Walk or cycle if you can

 


Monday, 12 October 2020

Day 210 of self-isolation - A grand day out

A grand day out.

I went to London on Sunday, to see the daughters and family. We discussed the usual subjects, with the exception of Brexit, which is a dead horse now.

For dinner, we had meatballs and rice.

I suspect that this might be the last time we can all get together for several weeks. 

And when we got home, we found that the heating system has failed.

 



Sunday, 11 October 2020

Day 209 of self-isolation - Duff server

Duff server

One of my servers failed. It failed by crashing. A cold boot got it working again; it crashed again after a few minutes. After trying that a few times, I knew that I had to fix it.

I took it out of the rack, put it on the workbench and opened it up. A temperature check showed no problem, so I replaced all the memory (memory can fail eventually) and took out the ethernet card. I started it up again, and now it failed during startup.

It's either the motherboard, the cpu or the power supply. I decided to shortcut the process, and replaced all three. The CPU and motherboard are quite old, and I have a dozen newer ones that I got as a job lot for £20 each, including memory, so I used one of those; faster cpu, better motherboard (it has gigabit ethernet) and more memory (8gb instead of 2gb). 

I could have reinstalled the operating system, but I thought, wotthehell and just put the hard drives from the old computer in. I gave it power, and it booted straight up! No need to install a new OS. One small problem; it didn't recognise the gigabit ethernet. So I checked ifconfig and it had actually recognised the networking, but was using DHCP instead of a hard-coded IP address. 

I installed NetworkManaget-tui and ran nmtui. I deleted the cards that it thought it had, and added the one it actually had, told it the IP address I wanted, and the DNS servers, and then it all worked fine.

Slight problem - this motherboard doesn't have an external serial port, because hardly anyone uses those now. But my temperature monitoring system uses a serial interface. There is a serial header on the motherboard, it just doesn't have a nine pin D-shaped connector. No problem, I have a boxful of cables with a header on one end and a nine-pin-D on the other, so I plugged that in.

And Thunderbirds are go!




Saturday, 10 October 2020

Day 208 of self-isolation - Situation in Europe

The Situation in Europe

In Spain, we're in the middle of the second wave. I'm glad to report that daily case numbers are on a strong downtrend, but the daily deaths are still rising  - the latest number is 241.

In France the second wave is still rising rapidly. The latest daily case number is 20339, about four times as many as in the first wave.

In Italy, the second wave is on a strong uptrend, and could soon equal the worst of March/April.

In Germany, the second wave is on a strong uptrend, and looks like it will reach the levels of last spring quite soon. 

In the UK we're on the second wave, and the numbers of new cases are about three times as much as last March/April, and still rising fast.

So it looks awful, but it's not as bad as it looks. The CFR (case fatality rate, the number of deaths divided by the number of cases) is a LOT lower than it was last spring. That's partly because we now have better treatments than we did back then, and partly because we're now detecting the virus much sooner. Meaning, not at the point when the infected person is already gasping for breath.

In the UK, the test-and-trace system seems to have completely broken; only 25% of conacts are being traced within a short period of time. That's what happens when you put a jockey in charge of an IT system.



Friday, 9 October 2020

Day 207 of self-isolation - Another trip

Another trip

It's looking increasingly likely that London is going to Defcon four, so before that happens, we're making another trip to see daughter.1 etc, because we didn't see her last trip.

This, of course, is conditional on there not being a lockdown before Sunday that prevents that. Because things are not looking good right now, with 17540 new cases yesterday, and another 77 deaths. And the curve of new cases is on a strong uptrend; deaths will follow a few weeks later. 

Meanwhile, in America the second round of Trump vs Biden looks to be cancelled, because no-one wants to get into an enclosed room with a disease carrier, so the cross-party committee agreed to have it virtual. But Trump chickened out of that - maybe the White House internet connection is a bit iffy.



Thursday, 8 October 2020

Day 206 of self-isolation - Trouble up North

Trouble up North

Manchester, Liverpool, Newcastle are facing additional lockdowns. Pubs and restaurants will be further restricted. This is because the priority is to keep schools and universities open.

Now that the "blocked spreadsheet" problem has been Dynorodded, a lot of cases have become apparent. As you can see from the chart, the number of cases is now well above the worst of last spring (before removing the blockage, the number was thought to be around 7000, but was actually 50% bigger and climbing. We still need to avoid swamping the hospitals.

Death numbers aren't as dreadful as last spring, because our world-beating government has now realised that we can't just dump infected people into care homes. Also, we now have much better knowledge of how to treat Covid. But anyone who does reach hospital, will still need care and attention, and there are bottlenecks such as the number of beds (Nightingale temporary hospitals help with that) and staffing, which isn't solved so easily. So deaths are up to 70 per day, a tenth of last April, but still rising in a very unpleasant way. And since deaths lag cases by a couple of weeks, I think that will get worse.

London has not been targetted yet for more restrictions, but I suspect that it will.

I'm sad for the pubs, restaurants, theaters and the whole hospitality industry, but if I had to choose between those and the education sector, I think our children's education is more important.

So do we have the option of just letting the virus rip through the population? Yes, of course we do. But whoever makes that decision, will have to live with their conscience owning a number (unknown) of additional deaths. 

I'm glad I'm not the decision maker.




Wednesday, 7 October 2020

Day 205 of self-isolation - Attack ads

 Attack ads
 
We don't have anything like this in the UK. Our elections are short and (mostly) about the policies and issues. American elections are long and brutal, and mostly about the shortcomings of the politicians.  
 
Nothing seems to be out of bounds. No dirt is buried too deep to be exposed. A baby kissed 50 years ago is reframed as a pedophile incident. Any trip or stumble is turned into an allegation of dementia.
 
And, of course, it's election season, so the attack advertisements are coming thick and fast. My favourites are from "The Lincoln Project". No punches are pulled, every silver lining has a cloud. The adverts are mostly a minute long, and are vicious, aggressive and accuse Trump of betraying America, killing Americans and giving the voters a stark choice - "It's Trump or America".  
 
I'd like to find a similar series of adverts attacking Biden, but I couldn't find any good ones. But I did find this collation of ads over the last 60 years, showing that attack ads are a long term American tradition.



Tuesday, 6 October 2020

Day 204 of self-isolation - Another shambles - uncounted cases

Another shambles - uncounted cases

16,000 cases of Covid went missing. For example, October 2 figures were 6868, and should have been 4786 more. This isn't just a statistics shambles, it also means that 4786 people did not have their contacts identified and notified. The whole point of test and trace is to be able to do that, and if you don't trace, the people who should have been contacted, aren't told, and if they were infected, will be out in the community merrily spreading the virus.

And how did this happen?

An Excel spreadsheet reached its maximum file size, so the automated process could no longer add more names. The maximum file size is 2 gb. If there are a million people in the database, and each person uses 2 kb of data, then you've hit 2 gb. How could anyone think that there would be less than several million people to get infected?

Aaarghhh!!!

And no-one noticed for several days.

This needs a database. What idiot used a spreadsheet? Spreadsheets are for small simple stuff. I use a spreadsheet to track my computers; some 200 of them, unlikely to rise to 300, file size is 100kb. The great thing about a spreadsheet is that anyone can use them, it's "programming power for the people". The terrible thing about a spreadsheet, is that many of the people using them have no programming or database experience, don't know what the limitations are, don't know about the need for debugging or how to do it and assume that "the spreadsheet is OK because I made it myself".

So, when I was looking at the case numbers for the last few days, it looked like the numbers had peaked and were slightly falling, which is very encouraging. But it turned out that this wasn't true - I had been misled by the inaccurate numbers - and so had the oven-ready policy makers in our world-beating country.

And, of course, Dido Harding is in charge of all this. Baroness Blunder herself. The Shambles-in-Chief who was in charge of TalkTalk when they had their huge IT failure. But it's just another instance of the UK government being unable to organise an IT project in a brewery.

 



Monday, 5 October 2020

Day 203 of self-isolation - a trip to London

A trip to London

We had a big day yesterday.

First we visited our local doctor for flu vaccination.  We whisked in and out, it was all very well organised - a sharp scratch and we're done, exit through a different door from the entrance.

Then home for a shower. We always shower and change after visiting medical places, because it might not have much effect, but it's easy and cheap. And after I got home, my new printer arrived.

My "old faithful" HP Laserjet 6P has served me faithfully for 30 years, as a printer. But it isn't a copier. And the printer that I use as a copier, has stopped working. So on Thursday evening, I ordered a Kyocera 1220 MFP, and on Saturday it arrived, which is very quick. But I left it until Sunday to install it.

Then we piled into the car and drove to London. Daughter.1 has a tummy upset, and although we don't think it's Covid, she decided to stay at home "out of an abundance of caution". So we visited daughter.2, Mr .2 and grandson.3, who can nearly walk, although I am assured that he can actually walk. I think he'll walk very soon; he just hasn't yet fully appreciated the advantages of bipedal locomotion over quadrupedal..

Then we ordered a takeaway dinner, which should have arrived within an hour, but two hours later I was staring starvation in the face, and even a packet of Hula Hoops didn't still the pangs of hunger. Eventually, we sent Mr .2 out to get pizza. And, of course, a few minutes after they were ready, the food arrived. It was very tasty, but we won't be ordering from them again, because the wait was so much longer than they had said.

Today, I tackled the new laser printer. It was pretty easy to set up, although I still haven't worked out how the paper width control sides work. I did set them to the right width, but I don't know how I did it. But when I went to stow away the manuals, I found a replacement roller and toner for the old machine. So maybe I can fix that.

Kyocera toner costs £67 per cartridge, but I found an alternative for £4 and ordered two.





Sunday, 4 October 2020

Day 202 of self-isolation - The Trump situation

The Trump situation

 As ever with politicians, and especially with Trump, there is the story that we are fed, and there is the truth. And since Trump has told a great many lies (one estimate puts it over 20,000) especially about the pandemic, we take anything that the White House says with a large pinch of salt.

So here's the official story. Trump tested positive on Friday. He had an "extremely mild cough", a blocked nose and tiredness.He was airlifted to the Walter Reed Medical Center, and he's still there. He has tweeted that "I am feeling well!"

And here's the truth. He was given an experimental, unapproved drug Regeneron, which is supposed to encourage the formation of antibodies. Personally, I would not be testing experimental drugs on the President of the USA, but I guess they do things differently there, and rightly assume that senior politicians are expendable.

Ironically, he has not been given hydroxychloroquine, or an injection of disinfectant, or a very bright light.

Saturday morning, Dr. Sean Conley said that Trump had tested positive 72 hours earlier, which put it at Wednesday morning. But then it was realised that this implied that Trump knew he was infected while he made his fundraising trip to New Jersey. When the implications of that sank in, Conley said that he meant that this was day three, and Trump wasn't diagnosed until after that fundraiser.

Conley said "He is not on oxygen." Translation - that means that, at this moment in time, he is not on oxygen, but rather leads us to think that oxygen has not been part of the treatment. It turns out that it was.

An inside source contradicted the "slight sniffle" story. "The President's vitals over the last 24 hours were very concerning and the next 48 hours will be critical in terms of his care. We are still not on a clear path to a full recovery," the source said.

So - make up your own mind. You can believe the person who, in February, knew that this was a serious air-transmitted pandemic, but chose to lie to Americans "to avoid panic".

Or you can believe the people who contradict him.

So, what will happen now?

The election of November 3, isn't going to be postponed. As long as Trump is alive, he will continue to be the candidate.

But he's always tried to project an impression of strength, and a week-long stay (at least) in hospital is contradicting that. His big rallies are all cancelled. His campaign has run out of money, on account of either fraud, or drunken-sailor-type spending in the last few months by his campaign management. And the worst thing is, the one big issue that he's been trying to ignore and pretend isn't any kind of big deal, has jumped up and bitten him really hard, and ensured that the big story in the weeks to come will the the pandemic.

I wish him a full recovery, just as I wish the other 7.5 million Americans a full recovery. And it will be so much better for America when he is crushed in the election than if he dies of the virus that he called a hoax.





Saturday, 3 October 2020

Day 201 of self-isolation - Infected Americans

Two more Americans got Covid

That brings the total of American infections to 7.5 million. We're seeing about 45,000 new infections per day in America (7,000 per day in the UK) and we wish them all a full and speedy recovery - but we also know that won't happen, many of them will die. Those two Americans are only a tiny fraction of this dreadful pandemic, but the old obese male of that pair is at greater risk - that's the way this virus works.

So let's face the facts. Boris Johnson came close; he spent time in the Intensive Care Unit, and recovering from that level of illness takes a long time. Boris was 56, male and overweight - all factors that lead to a higher death rate.

In wars, old men send young men off to die. In pandemics, it's the other way round. 

Donald Trump is 74, male and obese - look at his picture. His fatality percentage is 4 or 5%. Pot and kettle - I am too. There's nothing I can do about the first two, but I am slowly losing weight - I'm down to 16 stone 2 pounds now, and the NHS web site recommends that I lose another 11 pounds.

But I don't go to large indoor unmasked rallies. I wear a mask when I go out.  I wash hands after handling anything potentially infected. I'm reasonably careful. I don't think that this pandemic is  hoax. I don't get tested every day like he does, nor do the people around me. But despite that, the virus got him. It isn't enough to just hope you'll be fine, you also have to take precautions. So far, so good - I hope to stay uninfected until the vaccines become available and this long nightmare is over.

Tomorrow, I'm going for my flu jab, and then down to London to visit the daughters. There will be six people present. I'm being careful, following the rules, and I'm fine. I hope that the 35 million infected people around the world also recover, but a million have died already, and more will face the Grim Reaper before this is over.

 


Friday, 2 October 2020

Day 200 of self-isolation - The Three Stooges

The Three Stooges

 


You remember when Dominic Cummings blatantly broke the lockdown rules and got away with it, thereby granting licence to millions of us to follow his example and ignore the rules when it didn't suit us? He should, of course, have been fired. But wasn't. One rule for us, another rule for them.

The first stooge today was Jeremy Corbyn (hereafter referred to as Larry). As you can see from the picture, he's in a group of eight people (one behind the camera), flagrantly violating the rule of six, almost as if he believed that the rules don't apply to him. Larry should now be prosecuted for violating the Rule of Six - I think the fine is £200.

The second stooge was Stanley Johnson (hereafter referred to as Curly). Curly was found browsing in a shop without wearing a mask; this has been compulsory since July 24. So that's another £200 fine.


And the third stooge is Margaret Ferrier, hereafter referred to as Moe. Moe is the MP for Rutherglen and Hamilton West. On Saturday, she got the symptoms, and took a test. At that point, she should have self-isolated, but no. On Monday, she travelled 400 miles by train to London, a six hour trip, spraying virus particles as she went. Monday evening, she was told that her test was positive.

On Tuesday, she knew that she was infected with Covid-19. So did she self-isolate? Of course not. She got the train back to Scotland, spreading the virus as she went, like a kind of "Johnny Appleseed", but spreading virus instead of apple trees.

And just for added irony, Mo was one of those calling on Cummings to resign after his idiocy. “Dominic Cummings’ actions have undermined the sacrifices that we have all been making in lockdown to protect each other from coronavirus. His position is untenable and he must be removed from his post now … The public health advice is crystal clear. For the safety of others, anyone with coronavirus symptoms must self-isolate, in line with government guidance. They should not leave the house for any reason.”

She's been removed from the SNP, and people are callng for her to resign from parliament. Which she should. Because it should not be "One rule for them, another rule for us".

 





Thursday, 1 October 2020

Day 199 of self-isolation - Herd immunity

Herd immunity

What is herd immunity, and what do the numbers mean? Herd immunity is the situation when so many people in the "herd" are immune to the virus, that the virus can't find enough people to infect, and dies out. Historically, this has been the only way that epidemics can end.

There are two ways to be immune to the virus. The first way is to become infected. My immune system sees the invader, and does the necessary things to kill it. And it remembers via mechanisms that we've evolved, so that the next time it sees the same (or similar) virus, it can go straight into action and kill it before it affects the body. The other way is to "teach" the body about this new virus - that is called vaccination, or immunisation. There is a third way, of course, and this is to die, but none of us want that.

So what percentage of people need to be immune, to reach herd immunity? The calculation is really quite simple.

Let's call the average number of people who get infected from one infected person, R0. If R0 is less than 1 then the virus will die out, and the nearer it is to zero, the faster it will die out.

If R0 is exactly 1, then each person infects one other person, if it is slightly less than 1, the virus slowly dies out.

What affects R0? A number of factors, such as  how the virus spreads, and how many virus particles does it take for it to take root. So for example, if it spreads through the air, it will be more infectious than if it can only spread by shaking hands. We measure the R0 by observation, you can't calculate it from the virus genome.

So, consider a virus with an R0 of 2. Each person infects two other people. But if one of those two is immune, then that drops the number infected to 1, and the virus can't grow. So, clearly, herd immunity for that virus would be 50%.

If a virus has an R0 of 10 (measles is 15) then nine out of those ten would need to be immune, so herd immunity happens at 90%, and that's why public health people are so keen on measles vaccinations for everyone.

And since Covid-19 (the disease that you get if infected by SARS-CoV-2) has an R0 of 3, so herd immunity happens when 2 out of 3 are immune. Herd immunity happens at 66%.

More generally, we can use the formula 

Herd immunity percentage = 100 - 100/R0

So what happens when everyone wears a mask? Masking interferes with the transmission of airborne viruses. It works in two ways. First, if someone is infected, then a mask will trap most of the virus particles they are shedding, because it will trap the droplets that they are carried on (especially coughs and sneezes, but also ordinary breathing). Second, if someone is not infected, then the mask will reduce the number of virus particles that they breathe in, and so reduce the likelihood of the virus being able to establish itself in a new victim.

So, suppose that masking reduces virus spreading by half, and the R0 falls from 3 to 1.5. We can put that number into the formula, and we find that we reach herd immunity at 33%.

But it isn't going to be possible to persuade every susceptible person to mask, or even every infected person to mask, because often people don't know that they are infected. So, masking will reduce the spread of the virus, and the population reaches herd immunity at a lower level of immunity. Not-masking means that you don't get to herd immunity until a lot more people are infected.

Vaccination isn't going to be perfect either. Flu vaccines are never 100% effective, and the Covid-19 vaccines won't be either. But a bigger problem (in some countries) will be vaccine refusal. And the people who refuse vaccines might be the same ones that refuse to mask. Countries that have such people will, of course, suffer far more than people who take the sensible precautions of masking and vaccination, but what can be done about that?

The campaign against cigarette smoking was massively successful; UK men smokers fell from 82% in 1948 to 14% today. Why was that? People were told the facts, and shown the consequences of smoking. We need to do the same for vaccination and masking. Show the facts and show the consequences.