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A brief 
about COVID vaccines and testing and transmission and symptoms.
I’ve been hearing comments about how workers like those infected in the latest outbreak need to be vaccinated to prevent community outbreaks like what we’ve just had. THIS IS WRONG!
about COVID vaccines and testing and transmission and symptoms. I’ve been hearing comments about how workers like those infected in the latest outbreak need to be vaccinated to prevent community outbreaks like what we’ve just had. THIS IS WRONG!
While high-risk workers get weekly or fortnightly COVID tests, a lot of cases are found not through these scheduled tests but when these workers develop symptoms and seek unscheduled testing. That is, we find them because they are symptomatic.
All of the COVID vaccines that Aotearoa has scheduled are excellent at reducing symptoms in people exposed to COVID. They will prevent symptoms (and hence the terrible health consequences) in 90% or more of cases.
I.e. they turn infections from symptomatic into asymptotic cases.
I.e. they turn infections from symptomatic into asymptotic cases.
But there’s very little evidence that being vaccinated does much to stop _transmission_ of COVID.
One vaccine has one study that suggests that transmission is reduced to about half what it would be. For other vaccines, we have no good data. There’s a good chance they do nothing.
One vaccine has one study that suggests that transmission is reduced to about half what it would be. For other vaccines, we have no good data. There’s a good chance they do nothing.
This means that if individuals at high risk of exposure are vaccinated, you don’t reduce the chance of them getting infected or of transmitting COVID but you do massively reduce the chance that you will know promptly that someone is infected.
And this in turn _increases_the chance that they will infect other people. More so since they feel okay and keep interacting with people.
This means that vaccinating people at high risk of exposure actually _increases_ the likelihood of a community outbreak, unless you increase the frequency of testing for those people to something like every two days.
This isn’t to say that there aren’t other reasons why you should vaccinate people who are at high risk of exposure - like doing the ethical thing for people putting their health on the line for not great pay.
So, yes, prioritize vaccinations for our high-risk workers (& their families). But _only_ after we have found a way to test sufficiently to mitigate the increased risk of asymptotic transmission from them.
Addendum: the above applies in countries like Aotearoa where there is (mostly) no community transmission and the risk is of introducing infection through the border. If you’re in a country with rampant community Tx already - vaccinate away (but start w/ the medically vulnerable)
