After more than a year of fighting a highly transmissible and deadly virus, getting vaccinated against COVID is a moment of major relief. All three of the available U.S. vaccines—Pfizer, Moderna, and Johnson&Johnson—have been proven to be highly effective in protecting the general population against COVID. But the general population doesn't account for underlying conditions or factors that could affect how the vaccine works in certain individuals. As more research comes out, we're learning more and more about how some groups may produce reduced levels of antibodies after vaccination compared to others in the general population. While researchers are not yet sure exactly how antibody response translates into protection from the virus, a new study has found that your age could be one of these factors that reduce the antibodies you produce from the Pfizer vaccine.
The study, which was conducted by the Centers for Disease Control and Prevention (CDC) and published June 8 in the Emerging Infectious Diseases journal, looked at the antibody response in those who received the Pfizer vaccine. Researchers compared the response for 71 older adults with an average age of 81 years old and 123 healthcare workers in Germany with an average age of 34 years old.
According to the study, the younger healthcare workers consistently had higher antibody levels than the older group—even after everyone was fully vaccinated, two weeks after their second shot. At four weeks after the second dose, both groups had their highest antibody response rates, but the younger group still had significantly more pull than the older. The researchers found that more than 99 percent of the healthcare workers in Germany showed reactive IgG antibodies at this time, while only 91.4 percent of the elderly participants showed the same.
The researchers noted that a "small fraction of elderly participants did not demonstrate robust antibody and T-cell response," even at four weeks after their second dose.
"A booster vaccination, altered vaccine dose, or different COVID-19 vaccines should be considered for the elderly if further evidence demonstrates high rates of breakthrough infections despite 2-dose BNT162b2 (Pfizer) vaccination," the researchers concluded.
Pfizer has already been working on a booster vaccine. During a May 20 Axios event, Pfizer CEO Albert Bourla said that a booster shot may be needed as early as September or October for some Americans—particularly those who were in the first round of vaccinations, like older adults. Moderna CEO Stéphanel Bancel echoed this sentiment.
"People at highest risks (elderly, healthcare workers) were vaccinated in December/January. So I would do [a] September start for those at highest risk," Bancel said.
Older adults not only had reduced antibodies from the Pfizer vaccine, however. They also had delayed antibody responses. At week three after the first dose and just before the second, an antibody response was detected for nearly 87 percent of the younger healthcare workers. But a response was detected for only 30 percent of the elderly participants three weeks after the first dose, clearly "indicating a substantial delay and overall reduced antibody response in elderly participants," the researchers said.
This also shines a light on a problem with vaccination strategies focused on broadly administering the first dose of a two-dose vaccine series while postponing second doses. "This practice might leave a relevant proportion of elderly with comparatively low levels of immunity for a prolonged period, emphasizing the need for non-pharmaceutical interventions, such as mask use and regular testing," the researchers noted in their study.