The biology of coronavirus COVID-19 - including research and treatments

Every other vaccine has been tested on the basis of reducing symptoms, rather than reducing transmission. It just so happens that they're effective at doing the latter too.

None of the phase 3 vaccine trials are sufficiently powered to get a true idea about transmission rates - they'd need ten times as many participants, or much longer followup periods (the latter of which is probably unethical since the vaccines have demonstrated to be effective).

But we can guess.

The AstraZeneca vaccine (interim) data published in The Lancet showed that 14 days after the second dose, the efficacy was 55.7% for any positive result, including asymptomatic cases, compared to 70.4% against symptomatic cases. It is not unreasonable to expect a similar reduction against asymptomatic infections in the Pfizer/Moderna vaccines.

Note that a true 80% effective vaccine will need 75% of the population to achieve 'herd immunity, and a true 60% vaccine will need 100% to be vaccinated. See: https://www.medrxiv.org/content/10.1101/2020.12.15.20248278v2.full-text

It is debatable how effective the vaccine will be in reducing transmission from symptomatic cases. But no one should argue that someone who has no symptoms and tests negative (on PCR) is going to be infectious.

Which leads to the last topic - very few (natural) COVID cases are asymptomatic and asymptomatic spread is rare.

Household transmission of SARS-CoV-2 and risk factors for susceptibility and infectivity in Wuhan: a retrospective observational study
https://www.thelancet.com/journals/laninf/article/PIIS1473-3099(20)30981-6/fulltext
This study is based on a 'whole' set of contact tracing data between specific dates in Wuhan.

Looking at the raw numbers, 2% of the overall infections were reported as asymptomatic. Of the secondary infections only 0.3% were due to exposure to asymptomatic cases.

Given the difference in rate of infection in the different clinical severity groups, it may be reasonable to suggest that there could be a reduction in transmissibility even in the mild symptomatic (post-vaccination) cases compared to a naturalistic case (which may be more severe). In terms of asymptomatic cases, I'd expect at least a 90% drop in transmissibility, compared to a naturalistic unvaccinated COVID case, given the above data.

If there is a 25% drop in transmissibility in symptomatic cases post-vaccination a 90% drop in transmissibility for asymptomatic cases and an (overall) 15% efficacy gap between asymptomatic and symptomatic cases, then the efficacy against transmission of the Pfizer/Moderna drops to around 83% (from 95%) and the AZ vaccine drops to around 65% (from 70.4%).

These are not concrete numbers, but illustration of what could happen given the hypothetical risk of asymptomatic case transmission.

 

Apparently talking has a greater risk of spreading Covid-19 indoors than coughing does:

https://www.msn.com/en-gb/health/me...19-indoors/ar-BB1cVWXB?ocid=ASUDHP&li=AAnZ9Ug

 

Single dose of pfizer jab said to be less effective than expected, reported in the Guardian, hard copy 20/01/21. Link to Guardian article embedded in link below.

https://www.businessinsider.in/scie...us-and-uk-strategies/articleshow/80367765.cms

 

Wondering how/if this will affect U.K. vaccine rollout. Apparently I will eventually be invited to receive it at a local church hall at the end of the road. I am in group 4 (over 70) so theoretically this will be before 15th Feb although there are reports that over 70s are already being invited in some areas: doubt if it will be here since London is apparently slow to vaccinate. I have heard one report of a 78 year old being called there.

Just also heard that they have dispensed both pfizer and oxford vaccines which slightly surprises me since I thought pfizer would be dispensed through hospital clinics where temperature control could be maintained.

Suddenly feeling very impatient to start vaccination process after 11 months isolation. News of the local arrangements was slow to reach me because I am mostly cut off from sources of informal news and there are firm messages not to contact GP surgeries for info. It has made me very conscious and appreciative of the speed in getting this vaccine developed and distributed.

 

I think this is as much about who is vaccinated (eg at risk people), and the short followup periods (the clinical trials had 2-3 months followup time).
Still, I agree it means the delayed dosage strategy is flawed and we should not be complacent about the vaccine itself protecting elderly/at-risk people - we need herd immunity and quarantine measures to eliminate the virus to protect at-risk people.

 

It can happen with insect stings, so I'm guessing it is possible?

 

According to the Spanish newspaper, El País, Patrick Vallance is having serious second thoughts about giving people just one dose and waiting. The UK papers seem a bit more reticent so far.

 

student nurse in family booked in to get Pfizer first shot next week and follow up 4 weeks later

 

You mean the second shot 4 weeks later?

 

Covid: How a £20 gadget could save lives

https://www.bbc.co.uk/news/health-55733527

 

Interesting, I heard the interview with Patrick Vallance (originally broadscast on Sky - yesterday) earlier*, and he was talking about 89% efficacy after 10 days (single dose). Not sure where El País is getting it's info from.
I hoping a vulnerable family member (50s years old) is vaccinated soon - even a single dose might improve the odds enough!


*14.45 minutes - World at One Radio 4 - https://www.bbc.co.uk/sounds/play/m000rc4t

 

I have seen the El Pais story elsewhere. Vallance has certainly realised that the Israeli data cast significant doubt on any suggestion that a single dose has major efficacy. I strongly suspect that what is being fed through the UK media is being filtered. You can read an article on El Pais free if you get it up on the web. They are very often ahead and accurate.

 

Merged thread

Emergence and rapid spread of a new severe acute respiratory syndrome-related coronavirus 2 (SARS-CoV-2) lineage with multiple spike mutations in South Africa
Tegally et al. medRxiv (2021)

Nature: Fast-spreading COVID variant can elude immune responses

This new variant is potentially important wrt vaccine efficacy.

 

Yes. Booked at same time

 

Thanks I found it and yes there are some important qualifications:
Vallance (El Pais):
"in practice it [efficacy] will not be as high [89% - trial data], although not as low as suggested [33% - from Israel]---"

Believe it or not they also quote "Matt Hancock" who acknowledge that they still don't know the degree of protection afforded to those with underlying conditions.

 

Merged thread

Fauci is giving a WH news conference now and said they are a bit more concerned about South African variant than UK variant wrt diminished vaccine efficacy and monoclonal antibody treatment efficacy. He implicitly referred to this study.

Fauci described a “cushion effect” regarding vaccine efficacy, and based on initial evidence of SA mutant that there’s still more than enough cushion in current vaccine efficacy that it shouldn’t make enough difference when it comes to COVID illness after vaccination, though nothing said about post-vaccination transmissibility.

 

Emphasises how much better the situation is in Australia, New Zealand ---. Still I think they have to go for 1 dose strategy --- it might be enough to reduce then number of hospital admissions --- whether people with only 1 dose will still be at risk of serious infection (requiring hospitalisation) is not clear ----

 

Perhaps related to cosmetic fillers containing PEG being very popular in California?

 

BBC and others are quoting statistical evidence based reports that the new "UK" variant is at least 30% more lethal than the original.

https://twitter.com/user/status/1352686766290055169


IMHO this corroborates the transmissability data to some extent as you would expect a mutation purely for higher transmissability (via cell infection success or immune evasion as opposed to longevity in the environment or physical influences on dispersal aerosols) to cause higher rates of viral replication and therefore pathogenicity within an individual as well as between individuals.

Previously the government stated there was no evidence that the new variant was more lethal, presumably to avoid panic but this would appear to have conveyed an incorrect impression.

I have edited a previous post of mine which was based on that incorrect impression, to clearly reflect the reasons for the edit and the recent developments.
https://www.s4me.info/threads/the-b...vaccines-treatments.14022/page-61#post-315483

As my grandad used to say, the only thing worse than making a mistake is failing to learn from it. It would seem one had to bear in mind that no data is not the same as data of no effect to interpret the message in the media correctly.

A LSHTM spokesperson recently said there was no data that the new variant made the vaccines less effective, which by the same logic, is not the same as data that it does not.

So that must be viewed as an uncertain quantity and it follows it is possible that the new variant is less effectively blocked by vaccines, we simply dont know. But any effect is likely to be commensurate with the rise in lethality rates which are actually statistically quite low per infection. I am sure they will be trying to gather the necessary data ASAP but that is likely to take a while.

 

I think that's still a "may be" rather than a definite "is" at the moment, isn't it?

I'm pleased to see, though, that the UK Government's advisers are taking advice from elsewhere and having a rethink about waiting up to 12 weeks to administer the booster shot: it sounds as though that may be brought down to about half that, which I think I'd be rather happier with.