Why doesn’t natural immunity count in the US?
Gandhi included a list of some 20 references on natural immunity to covid in a long Twitter thread supporting the durability of both vaccine and infection induced immunity. Marks added, referring to antibodies, that "Generally the immunity after natural infection tends to wane after about 90 days."23."It appears from the literature that natural infection provides immunity, but that immunity is seemingly not as strong and may not be as long lasting as that provided by the vaccine," Alfred Sommer, dean emeritus of the Johns Hopkins Bloomberg School of Public Health tells The BMJ.But not everyone agrees with this interpretation. Comparing the T cell response in people with symptomatic versus asymptomatic covid-19, Bertoletti's team found them to be identical, suggesting that the severity of infection does not predict strength of resulting immunity and that people with asymptomatic infections "Mount a highly functional virus specific cellular immune response."25.Already complicated rolloutWhile some argue that the pandemic strategy should not be "One size fits all," and that natural immunity should count, other public health experts say universal vaccination is a more quantifiable, predictable, reliable, and feasible way to protect the population. For people who did not have a confirmed positive result but suspected previous infection, reliable antibody tests have been accessible "At least since April," according to Klausner, though in May, the FDA announced that "Antibody tests should not be used to evaluate a person's level of immunity or protection from covid-19 at any time."26.Unlike Europe, the US doesn't have a national certificate or vaccination requirement, so defenders of natural immunity have simply advocated for more targeted recommendations and screening availability-and that mandates allow for exemptions. "As we continued to put effort into vaccination and set targets, it became apparent to me that people were forgetting that herd immunity is formed by both natural immunity and vaccine immunity," says Klausner. Another polarising factor may have been the Great Barrington declaration of October 2020, which argued for a less restrictive pandemic strategy that would help build herd immunity through natural infections in people at minimal risk.28 The John Snow memorandum, written in response, stated "There is no evidence for lasting protective immunity to SARS-CoV-2 following natural infection."29 That statement has a footnote to a study of people who had recovered from covid-19, showing that blood antibody levels wane over time. "If natural immunity is strongly protective, as the evidence to date suggests it is, then vaccinating people who have had covid-19 would seem to offer nothing or very little to benefit, logically leaving only harms-both the harms we already know about as well as those still unknown," says Christine Stabell Benn, vaccinologist and professor in global health at the University of Southern Denmark.