To what extent does getting another shot of our best COVID vaccines reduce your risk of infection? For arguments sake, say comparing folks with a shot 2-8 weeks ago vs. 3+ shots >12 months ago.

Will research and share links to serious studies after the poll closes.

Best evidence I can find suggests the answer is probably around 50%, maybe a little higher. That is, getting a recent shot cuts your risk of infection in half! I think most folks are under-appreciating this, leaning too much into “vaccines don’t prevent infection”. Some data:

In this study, a serosurvey (antibody test) was done for >5000 people in Hong Kong and correlated to their time of last vaccination. A recent 4th dose conveys ~75% protection, while 3 doses >200 days is ~20%. https://www.nature.com/articles/s41591-023-02219-5

Here’s a meta-analysis that looked at 18 of the best studies (covering 6.8 million subjects). It found a similar pattern of VE being high around 85% for the first 75 days or so, then falling to below 50% after 150 days. https://bmcinfectdis.biomedcentral.com/articles/10.1186/s12879-022-07418-y

It’s just an anecdote, but I’m in the middle of a bit of a personal test of this. My wife and I went to Vegas for our anniversary. I made time for a shot a week before going, she did not. We both went to all the same places and wore masks at the same times. And…

As soon as we got home, she tested positive and has been really sick for several days now. I have not. I thought I had gotten it from her (felt a sore throat yesterday) but feel fine today and still negative!

I get folks like @profvr saying 3 doses is enough for healthy people. But even if it’s not life threatening, being sick can REALLY suck! With the very low adverse reaction rate for 4+ doses, I, for one, will be getting mine twice a year!