COVID-19: Boosters Not Only Replenish Transmission Immunity, But Also Lift It, New Data Finds | UK News


Before I get into the numbers, here’s something important to keep in mind.

When people talk about whether vaccines work or not, they often mean two things. There is the extent to which a vaccine can protect you against infection: will it prevent you from catching COVID? And there’s the protection a vaccine gives you against serious harm: if I catch COVID, will that prevent me from going to the hospital or dying?

A person receiving a COVID-19 jab

These two types of protection – against transmission and against serious illness – are both very important, but they are also very different. Just because a particular vaccine is good in one area does not mean it is just as good in another. Just because a particular vaccine’s effectiveness in preventing transmission necessarily decreases does not mean its effectiveness in preventing serious disease decreases at the same rate.

I say all of this not only because the two types of protection are often confused (although they are) but because keeping that distinction under your hat is quite important when navigating all the data around COVID and vaccines. .

And to be absolutely clear, the majority of what is below relates to this first type of protection: transmission protection.

As you probably know, the big picture here is that transmission immunity has recently waned. Here is one way of looking at it. If you received AstraZeneca vaccine, its ‘vaccine effectiveness’ (an epidemiological term meaning the extent of protection it gives you compared to an unvaccinated person) was 92% right after your second dose. But over the following weeks, that immunity wanes, dropping to 69.7% at week 20.

The protection afforded by AstraZeneca was initially lower at 63% right after the second dose, dropping to 47.3% at week 20. Now these numbers are specifically for the Delta variant. From what we know, these vaccines were a bit better (much better in the case of AstraZeneca) at protecting, for example, the Alpha / Kent variant. Even so, it is clear both that they are not as high as everyone would like and that they are falling.

Which brings us to new data released today by the UK Health and Security Agency (better known as the agency formerly known as Public Health England) on the first evidence of the UK’s recall program. The news here is very promising. He suggests that two weeks after a booster dose of Pfizer, those who originally received two doses of AstraZeneca are up to 93.1% protection and those who originally received two injections of Pfizer are up to 94%.

London, UK - March 19, 2021: People walk past a Covid-19 vaccination center sign outside Westminster Abbey.
People walk past a COVID-19 vaccination center sign outside Westminster Abbey.

In other words, it’s not just that the boosters replenish this immunity, they raise it beyond what it was at two doses – a little higher for the Pfizer team and much higher for the Pfizer team. the AstraZeneca team.

Now it is still early. We don’t yet know much about the difference boosters make when it comes to the vaccine’s other kind of efficacy: protection against hospitalization and death.

But as far as we can judge from the available data, the two main British vaccines – but especially the Pfizer vaccine – have seen this type of protection decline much less rapidly than the other type. It’s encouraging. This implies that those who have received two doses retain good protection against serious illness, even if their protection against transmission has diminished.


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