A simple blood test may help doctors determine how protected a vaccinated patient is against COVID-19. A group of researchers recently published a pre-print paper on the correlation between the Moderna mRNA vaccine and markers of protection against the virus in blood samples. This can be a valuable tool for developing future vaccines and to establish just how long our current vaccines provide immunity against COVID-19.
According to STAT News, these markers of protection include antibodies, types of cells, and other indicators in the blood that could help measure a person’s level of immunity.
“We saw a very clear correlation that the higher the level of antibody produced by vaccines, the less likely you were to become sick with COVID-19,” said Christopher Houchens, director of the countermeasures division of the Biomedical Advanced Research and Development Authority (BARDA), who was one of the study authors.
The team of researchers from U.S. health agencies, as well as academic circles, is also studying other vaccine responses, joining scientists from around the world who want to evaluate the use of measuring antibody levels in the blood to determine just how well various vaccines work to protect against COVID-19.
The advantage of using blood tests, according to STAT News, is that future vaccine manufactures would not have to enlist thousands of volunteers for their trials. If a certain level of antibodies determines protection against a virus, they would only need to recruit a few hundred participants. Once that level is reached, the vaccine would be deemed effective. For example, flu shots do not go through clinical trials annually. They are authorized based on their efficacy of protection in much smaller studies.
“Knowing the correlates of protection is incredibly useful,” said Angela Rasmussen, a virologist at the Vaccine and Infectious Disease Organization at the University of Saskatchewan. “It really helps us develop policies that maximize keeping people as safe as possible.”
Houchens adds that once that level of protection is identified by using a blood test, scientists can use that marker as a cutoff measurement. Anyone who has that level of antibodies, either induced by vaccine or by natural infection is protected, says Houchens.
According to NPR, knowing that cutoff level, also called the cutoff titer, is also a useful tool for establishing how long vaccine protection lasts. If the titer remains above the immunity threshold after 18 months, the vaccine is still working.
The researchers found, not surprisingly, that the higher the titers were for people who got the Moderna vaccine, the more protected they were. Conversely, when their titers signaled a low level of antibodies, the more likely vaccinated individuals were to have breakthrough infections of COVID-19.
Blood tests could additionally help identity people who require a third, or booster, dose of the mRNA vaccines. If certain groups experience a drop in antibody levels and begin to see cases rising in their sectors, it can help health officials authorize appropriate booster shots.
“We can track these individuals and look at if their antibody titers start to go down, but we don’t know how far they have to go down at this point to say, ‘Well your risk of infection is significant enough that we would recommend a third vaccine,’” said Houchens, according to STAT News.
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