“If it were the case that in London the disease hadn’t disseminated too widely, and only 15% have experienced the virus [as serology tests indicate] . . . under those circumstances, if you lift lockdown, you should see an immediate and commensurate increase in cases, as we have observed in many other settings,” Gupta told
The BMJ, “But that hasn’t happened. That is just a fact. The question is why.”
Possible answers are many, she says. One is that social distancing is in place, and people are keeping the spread down. Another possibility is that a lot of people are immune because of T cell responses or something else. “Whatever it is,” Gupta added, “if there is a significant fraction of the population that is not permissive to the infection, then that all makes sense, given how infectious SARS-CoV-2 is.”
Buggert’s study in Sweden seems to support this position. Investigating close family members of patients with confirmed covid-19, he found T cell responses in those who were seronegative or asymptomatic.
10 While around 60% of family members produced antibodies, 90% had T cell responses. (Other studies have reported similar results.
27) “So many people got infected and didn’t create antibodies,” concludes Buggert.
