This is the most promising data on COVID-19 antibodies and immunity yet

Some hopeful news has come out right before the long weekend. Two new studies have elevated the potential of antibody resistance, with detailed analysis. 

The herd immunity theory might be the most promising end to the Covid-19 pandemic and the most divisive one among medical professionals. 

In short, when a pathogen exists within a community for long enough a high proportion of individuals can become immune to its ensuing diseases. This in turn causes recovery rates to outpace transmission rates. The mechanisms that facilitate this process are varied but vaccination bears the most influence on its success rate. 

The two papers were conducted by a team of researchers at Harvard Medical School, Beth Israel Deaconess Medical Center, and the Massachusetts Consortium on Pathogen Readiness (MassCPR).

“The global COVID-19 pandemic has made the development of a vaccine a top biomedical priority, but very little is currently known about protective immunity to the SARS-CoV-2 virus,” senior author Dan Barouch explained in a press release, “In these two studies, we demonstrate in rhesus macaques that prototype vaccines protected against SARS-CoV-2 infection and that SARS-CoV-2 infection protected against reexposure.”

This first study analyzed 35 rhesus macaques monkeys after splitting them into two groups. The first group received one of six DNA coronavirus vaccine trials, and the rest were given placebo drugs. These monkeys were subsequently exposed to SARS-CoV-2.

Eight of the 25 vaccinated monkey models evidenced no detectable virus after exposure, while the others showed very low levels of the virus. 

The level of antibodies present in a model was determinative of viral load; the higher the antibody count, the lower the virus count. 

As previously covered by Ladders, the lower the viral load in an individual the milder the symptoms should they manifest at all. 

Similarly, organisms need to be exposed to a specific infection dose to become ill from a virus. This research suggests antibody resistance could effectively curb the amount of virus present in a host at the time of exposure. If this proves to be consistent on a communal scale, the number of disproportionately affected individuals will gradually decline and be absorbed by the majority of mild cases. 

In the second study, the team extended their research to determine if the same species of monkeys had developed a natural-biological immunity to reinfection. 

Nine adult macaques were exposed to the virus before experiencing and recovering from viral pneumonia. These developed coronavirus antibodies within 28 days.

Exactly one week later, the monkeys were exposed to SARS-CoV-2 again except this time they demonstrated a nearly impenetrable defense against reinfection.

After reviewing nasal swabs and bronchoalveolar lavage following reinfection,  the researchers observed traces of the virus consistent with exposure, but the levels declined rapidly and there was no recoverable virus in test samples. The monkeys developed immune responses to the virus so quickly they didn’t even become ill before the complete viral clearance. 

 “Little or no clinical disease was observed in the animals following rechallenge,” the authors explained. “SARS-CoV-2 infection in rhesus macaques induced humoral and cellular immune responses and provided protective efficacy against SARS-CoV-2 rechallenge. “These data raise the possibility that immunologic approaches to the prevention and treatment of SARS-CoV-2 infection may, in fact, be possible.”

These findings do not stand alone. A recent study conducted in China on the very same species of monkeys concluded immunity almost certainly protects monkeys from re-infection  Unfortunately,  no study has been able to determine how long a species remains protected against SARS-CoV-2 after initial exposure. 

The most substantial pillar from these two new studies and preceding Covid-19 antibody literature is their effect on viral load and case severity. 

Monoclonal antibody drugs currently in development will save lives and lessen the prodromes attached to critical manifestations of Covid-19.

CW Headley is a reporter for the Ladders and can be reached at