Please don’t call it “breakout cases” — vaccinations have two effects on the body’s immune system: first, there’s the “training” of our adaptive response, meaning that next time the invader (SARS-CoV-2 in this case) is encountered, our body can mount a much faster response. Secondly, for a while after the infection/vaccination1 antibodies float in your blood.

We call this serum-Ig and it’s a pretty cool thing. Essentially, we get ready for a reinfection within days or weeks, thus actively fighting pan-, epi- and endemics by creating super-stops. After two, three, weeks, this serum antibody level wanes. Our body is still able to respond quickly thanks to “memory cells” remembering the invader and being quickly able to spring back into action to create serum-Ig, but that takes a day or three, depending on the situation and the health of the responding system.

Simply speaking, we evolved to deal with emergent threats in small communities fast and efficiently, but our bodies didn’t adapt to world travel and communal mixing. Schaller et al (2009) called this the “behavioral immune system” and it’s thought to be the reason our brains react more favourably to people who look like us than those who look “different” or are “others.”

In small communities a three week “super-response” is sufficient. In larger ones with pockets it is not. So our bodies have to decide between the “costly” maintenance of serum-Ig or allowing invaders to roam for the 48-92 hours it takes to rebuild that.

This is why we wait between vaccinations: we want to create more memory cells, something that would not happen if the recipient’s serum still had many antibodies in it.

So after three to five weeks past a vaccination or infection you’ll still feel the effects of being infected. Much, much, less vehement, and much, much, less long (2-3 days instead of 14-20 days), but you’ll be infected and you can infect others. Of course once this happened, you’re a “super responder” for another 3-5 weeks, just whacking the invader as it enters.

So, this is why we still need to mask up: you could be infected, even though you have been vaccinated. You could pass it on to others. But you very likely won’t get sick and with a 98% chance won’t get severely sick, even if your serum antibodies are gone. And you’ll be right as rain in 2-5 days of mild symptoms rather than winding up in my ICU with a tube in your neck.

But those cases of vaccinated people with tested infections, some of which even feel a little under the weather… they’re not “breakout infections,” they’re just how our immune system works. Even vaccinated people can and will get infected. However, once the virus is nothing but a three-day cough and mild fever and tiredness we can say we won.


  1. Which are functionally the same to the immune system but vastly different otherwise. [return]
Mikka Luster @mikka