Evaluating necessity of Covid-19 vaccination in previously infected individuals • Hacker News Board

Re: Evaluating necessity of Covid-19 vaccination in previously infected individuals

#301

Post by HPsquared » Thu, Jun 10, 2021, 11:39 AM UTC

iso1210 wrote: post #266

sgt101 wrote: post #262

Earlier quoted context omitted.

According to this study it could be a long time before we know that - I think cov-19 in the presence of a non overwhelmed medical system armed with steroids and oxygen kills less than 2/100 infected folk so getting enough incidents in either of those arms of a trial is going to be hard work.

The death rate for certain demographics (especially say over 70s) is far higher than 2-in-100. While some countries have high levels of vaccination - especially in those demographics - most don't. The UK is enterring a third wave, and has a high number of elderly people having been fully (2 shot, mainly AZ) vaccinated. Early indications are that those enterring hospitals now on the whole have not been fully vaccinate…

The infection fatality rate varies exponentially with age. A good rule-of-thumb is that for a given age group, the IFR of catching Covid is about the same as the all-cause mortality risk over one year of life. It just so happens that these two numbers are about the same, when looking at age groups.

Edit: nicely presented here: https://www.bmj.com/content/370/bmj.m3259

Re: Evaluating necessity of Covid-19 vaccination in previously infected individuals

#302

Post by mnw21cam » Thu, Jun 10, 2021, 11:41 AM UTC

spion wrote: post #88

reducesuffering wrote: post #2

Punchline: “The cumulative incidence of SARS-CoV-2 infection remained almost zero among previously infected unvaccinated subjects, previously infected subjects who were vaccinated, and previously uninfected subjects who were vaccinated, compared with a steady increase in cumulative incidence among previously uninfected subjects who remained unvaccinated. Not one of the 1359 previously infected subjects who remained u…

I know that seems like a large number but in the vaccine arm there were 20x more subjects and only 15 cases. So with the 1359 previously infected subjects, assuming identical behavior to vaccinated subjects, we would expect around 0.9 cases if vaccines were approximately equal to infection. So this study doesn't have enough statistical power to say how vaccines compare to previous infection. Could be better, could be…

Here are the numbers:

Total participants: 52238.

Previously infected: 2579, of whom 1220 vaccinated, 1359 not vaccinated. No subsequent infections in either of these groups.

Not previously infected: 49659, of whom 29461 vaccinated (15 subsequent infections), 20198 not vaccinated (2139 subsequent infections).

Comparing previous infection with vaccination, we have 0/1359 infections in the previously infected and 15/29461 infections otherwise. According to Fisher's exact test, the two-tailed P-value for this is 1.0, which is very much not significant. You're correct to say that the study doesn't show how vaccines compare to previous infection. The study is way underpowered to show that.

For the unvaccinated, it gets more interesting. We have 0/1359 infections versus 2139/20198. According to Fisher, that has a P-value of 2 * 10^-64, which is most definitely significant. The study is not underpowered to show this at all. A previous infection is definitely protective.

With the caveat that the participants didn't have asymptomatic screening, so there is quite possibly bias due to people with a previous infection getting a second milder case and not being tested.

Using the exact method, 95% confidence intervals for infection rate are:

Previously infected, not vaccinated: 0% to 0.3%

Previously infected, vaccinated: 0% to 0.3%

Not previously infected, not vaccinated: 10.1% to 11.0%

Not previously infected, vaccinated: 0.03% to 0.08%

Re: Evaluating necessity of Covid-19 vaccination in previously infected individuals

#303

Post by iso1210 » Thu, Jun 10, 2021, 11:43 AM UTC

benjaminwootton wrote: post #294

iso1210 wrote: post #266

Earlier quoted context omitted.

The death rate for certain demographics (especially say over 70s) is far higher than 2-in-100. While some countries have high levels of vaccination - especially in those demographics - most don't. The UK is enterring a third wave, and has a high number of elderly people having been fully (2 shot, mainly AZ) vaccinated. Early indications are that those enterring hospitals now on the whole have not been fully vaccinate…

And for most people under 70, it's way under that, FWIW.

It does suggest that people with 2 shots are unlikely to end up in hospital. I haven't seen enough data about the hospitalisations when adjusted for age+vaccines to draw any more conclusions.

There are still many over 70s who haven't had any shots though. My (estranged) uncle and his mother-in-law haven't left the house for 18 months, he disinfects his food deliveries and leaves the post in a box for 3 days. He refuses to get the vaccine because he's worried about catching it. Chances are he won't end up in hospital either, but people like that could skew the cases as more data comes out to allow spurious claims from anti-vaxers (They might claim that 'before 2 in every 100 over 80s were going into hospital) , now it's only 1 in every 100 unvaccinated over 80s going in to hospital), because the chance of catching covid from the population still unvaccinated dwindles because of continued isolation

Re: Evaluating necessity of Covid-19 vaccination in previously infected individuals

#304

Post by galoisgirl » Thu, Jun 10, 2021, 11:44 AM UTC

marton78 wrote: post #295

galoisgirl wrote: post #293

Earlier quoted context omitted.

People in the same household have high chances of infecting each other.

Please read that comment again, it's about RE-infection

I know it is, my point is that two spouses getting re-infected isn't two independent things.

It's not like bringing your bomb onto a plane decreases the odds of an attack, because what are the odds of two bombs.

The devil is in the details here. If natural immunity wears off after 6-9 months (as some studies suggest), and one spouse got infected again after that period, then the odds of the other one of getting re-infected too are pretty high.

Re: Evaluating necessity of Covid-19 vaccination in previously infected individuals

#305

Post by alok-g » Thu, Jun 10, 2021, 11:55 AM UTC

bvinc wrote: post #137

This is really good news. Whenever I see people talking about if previously infected people should be vaccinated, they always mention how we don't know how long protection lasts for previously infected people. This study includes this section: Duration of protection This study was not specifically designed to determine the duration of protection afforded by natural infection, but for the previously infected subjects…

Re: Evaluating necessity of Covid-19 vaccination in previously infected individuals

#306

Post by paedubucher » Thu, Jun 10, 2021, 11:56 AM UTC

jokethrowaway wrote: post #287

paedubucher wrote: post #226

Earlier quoted context omitted.

Getting a vaccination just for "the points" looks like a bad idea to me, because "the health" should be the only point to be considered.

Welcome to regulations-ville, where nothing makes sense and clueless bureaucrats decide how many times you need to jump to get your freedom

Glad to see that I'm not the only one thinking this way.

Re: Evaluating necessity of Covid-19 vaccination in previously infected individuals

#307

Post by nradov » Thu, Jun 10, 2021, 12:31 PM UTC

ping_pong wrote: post #228

nradov wrote: post #187

Earlier quoted context omitted.

The most accurate approach would be to do repeated blood tests of a large nationwide study population looking at both antibodies and memory T cells. The CDC really should have been doing that nationwide for the past year.

How can you do that with over 50% of the population fully vaccinated?

The point is that they should have been doing that since tests were first available, before anyone was vaccinated. Even now it would still be a useful study in the unvaccinated population.

Re: Evaluating necessity of Covid-19 vaccination in previously infected individuals

#308

Post by FearlessNebula » Thu, Jun 10, 2021, 12:36 PM UTC

daenz wrote: post #128

Why is it that so many people seem to be biased against evidence that our immune systems do a pretty good job? It's as if they want the vaccine to be the only thing that helps stop COVID.

I think many of us are so exhausted from fighting to get people to just sort of follow the rules. I’d rather just tell everyone to get the vaccine and leave no room for error here

Re: Evaluating necessity of Covid-19 vaccination in previously infected individuals

#309

Post by snakeboy » Thu, Jun 10, 2021, 12:59 PM UTC

iso1210 wrote: post #267

thombat wrote: post #253

Earlier quoted context omitted.

Recently greek letters were introduced to remove the geographic stigma [1] , so that would read as "the Alpha strain now being the main one in Sweden" Besides risking moral overtones ("the British strain? Typical - when they aren't being Hollywood baddies they're busy incubating viruses") it only tagged where a strain was first isolated, not necessarily its geographic origin (not that it actually matters whether the…

It's quite amusing that there was such a push at the start of the pandemic to not call it Chinese Flu or Wuhan Flu, but the British, South Africa, India and Brazil strains all caught on quickly in the media.

I wonder which political variable could have left office between then and now to explain that?

Re: Evaluating necessity of Covid-19 vaccination in previously infected individuals

#310

Post by stordoff » Thu, Jun 10, 2021, 1:03 PM UTC

waterside81 wrote: post #70

stavros wrote: post #28

Earlier quoted context omitted.

That's encouraging! I got COVID a few months ago and got vaccinated recently, seems like I should be unstoppable now.

Hey I'm curious, if you don't mind sharing, how do you think you got it? Throughout this whole pandemic, I'm still kind of amazed how people are getting it

Almost certainly[1], my grandad caught it in hospital, then infected most of the rest of the family (6/7 people) when he was discharged.

He was admitted with suspected sepsis, and tested negative on admission. He had a new cough when he was discharged, but we didn't think much of it as he had COPD so periods of coughing weren't unusual. A few days later, he was readmitted with a recurrence of his original symptoms, but this time his admission test was positive. Six of the other family members tested positive the next day, and developed symptoms over the following days.

[1] The only other person in the house who hadn't been isolating subsequently tested negative. Everyone else had been nowhere but home for at least the proceeding two weeks, so the chance of another vector seems remote.