Sloppy Reporting Spreads Panic About Declining COVID-19 Antibodies
A July 11, 2020 preprint, “Longitudinal Evaluation and Decline of Antibody Responses in SARS-CoV-2 Infection,” authored by researchers at King’s College London, shows that the levels of SARS-CoV-2 neutralizing antibodies in the blood decrease, sometimes at a relatively rapid rate, only weeks or months after recovering from COVID-19. This finding has led some media outlets and scientists to conclude that a vaccine may not be able to provide lasting immunity; the San Francisco Chronicle reports that this finding “reinforced a decision by scientists at the University of California San Francisco and affiliated laboratories to focus exclusively on treatments [rather than vaccines].”
But does a decline in antibodies necessarily imply a loss of immunity? Should we lose hope for developing a vaccine?
The July 11 article itself includes several caveats:
Immunity is not all-or-nothing. The article references an alphacoronavirus study, which showed that although people could technically be infected a second time (as measured by reproduction of the virus in the body and viral shedding), “individuals showed no cold symptoms.”
This coheres with studies on rhesus macaques deliberately infected with SARS-CoV-2. There was evidence of viral reproduction when they were exposed to the virus a second time (one month later), but at levels far far lower than their initial infection, and causing no observable symptoms. Being “infected” for one or two days with no symptoms (good for the patient) and low levels of viral shedding (dramatically decreasing the risk of contagion) would be nearly equivalent to absolute immunity.
The authors write: “Taken together, despite the waning nAb [neutralizing antibody] titres in individuals, it is possible that nAb titres will still be sufficient to provide protection from COVID-19 disease for a period of time.”
Also — and incredibly importantly — a declining level of antibodies does not necessarily mean a significant decline in the ability to create new antibodies. “For those with a low nAb response, titres can return to baseline over a relatively short period.”
And antibodies themselves are not the only component of the immune response! The presence and longevity of B cells — able to produce additional antibodies when needed and often living for decades — and T cells, which target the virus and cells infected by it, absolutely must be understood in addition to passively measuring antibody levels in recovered individuals.
This study should absolutely not be taken as proof that the search for a vaccine is hopeless. Even if periodic booster shots are required, vaccines should still be effective.
