Quote:
Originally Posted by jfman
Is the Pfizer data from Israel not supporting that it reduces transmission?
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The simple answer is 'sort of/maybe' at this point. What is known is that the Pfizer vaccine reduces symptomatic and, importantly, asymptomatic infections. There also seems to be some good evidence coming out that the virus is cleared more quickly in infected vaccinated people.
If you think about how you get infected with SARS-COV2, you need to get close enough to someone who is shedding virus and breathe in virus particles in a high enough dose. Symptomatic people are a huge issue and they will coughing away and shedding a lot more virus in to the air so not only is virus coming out, it's getting forced out at speed (evolution is great!) BUT, at this stage, if you are symptomatic, in all likelihood you are going to think 'Uh oh, COVID' and isolate and get tested. Also, masks will help catch the droplets being sprayed out by a symptomatic person.
Logically, an asymptomatic person will be less infectious as they aren't coughing but the evidence is weak right now on how much less infectious they are. Kids are more likely to be asymptomatic, hence the in school testing going on right now (I have a big stack of test kit boxes on my dining room table right now for home testing of the kids) Te downside of asymptomatic people is that they are not isolating - they are merrily going about their way shedding virus. What we need to know is what the 'R' value is for an asymptomatic person and that isn't clear right now.
So, vaccines seem to reduce the numbers of people actively spreading SARS-COV2 by coughing and the numbers of people unwittingly spreading infection and the infective period seems less so, in all likelihood, vaccines will reduce transmission as there are less people spreading the virus. What is less clear is how infectious you are if you are vaccinated but infected. This is one of the reasons why the Government is asking vaccinated people to not go crazy (there are other behavioural reasons too of course)