Why So Many Vaxxed People are Getting It and Why Those Antibody Tests Look Increasingly Useless

 

Unless you have no friends, you probably know a lot of people who are vaxxed and boosted and nonetheless are getting infected. If the vaccines work, how can this be?

A recent article on the CBS News site asks and answers this question. In a nutshell, current variants have evolved to evade the antibodies generated by vaccines (and previous infections). And those tend to wane after a few months anyway. 

That means you can get infected even if you're vaxxed and boosted. But the vaccines are still doing their job of priming your immune system to prevent a serious illness if you are infected.

Vaxxed people feel protected from the virus so they let their guards down. They return to risky behavior like eating in crowded restaurants, not wearing masks in public, and so on.  

Combine this with a more infectious variant and it's a recipe for a lot of mild infections in vaxxed people. I know a lot of people who have gotten infected recently. To a person they describe it as similar to a bad cold.

This includes a family of five who have three kids under five years old. They recently got infected for a second time. But this time, the dad never tested positive on those in-home tests. An article on today's New York Times talks about a similar family, and it makes me wonder if those tests are worse than useless.

The article is not paywalled so you can read the details for yourself. But the upshot is that for many vaxxed people, their immune system is keeping the virus at low enough levels that it can't be detected on those tests. 

But these people can still display symptoms. Why? According to the article many of the symptoms people experience are not from the virus itself, but from the immune system activating to fight the virus.  So you can be infected and feel sick, but not have enough virus to trigger the test. 

I have blogged before about how those lateral flow antigen tests are of questionable accuracy. They have high false-negative rates for people who are symptomatic (around 25% for one brand I looked at) and are basically no better than a coin flip for people who are asymptomatic. 

If we now know that they also don't work very well for people who are vaxxed either, what good are they? One answer by a public health professional in the NYT article is that if you don't have enough virus to trigger the test, you're probably not very infectious either.

That's nice, but it doesn't mean the tests are any more informative about whether you have it or not. Personally, I will just stick with PCR tests if my goal is to determine whether I've been infected or not.



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