Researchers from the U.S. showed that antibody production in people vaccinated with Pfizer and Moderna dropped dramatically six months after vaccination. Antibody titers in those who received the Johnson & Johnson vaccine, however, remained stable for eight months. An article by scientists evaluating the immune response induced by the three vaccines was published in The New England Journal of Medicine.
Experts from Beth Israel Deaconess Medical Center and the University of North Carolina at Chapel Hill compared antibody and T-cell production in 61 people. Thirty-one of them received the Pfizer vaccine, 22 received Moderna, and eight received Johnson & Johnson. Measurements were taken from the second to fourth weeks after full immunization (receiving a single dose of Johnson & Johnson or a second dose for mRNA vaccines) through the eighth month.
"The mRNA vaccines were characterized by a high peak antibody response, which dropped dramatically by the sixth month and whose drop continued by the eighth month," says Dan Baruch, one of the researchers, director of the Center for Virology and Vaccine Research at Beth Israel Deaconess Medical Center. Meanwhile, the titer of neutralizing antibodies in response to the Pfizer drug was higher and more prolonged. Despite the fact that antibody production after Johnson & Johnson vaccination was initially relatively low, it remained stable throughout the entire observation period, the researchers note.
However, the researchers emphasize that the minimum levels of antibody production needed to provide protection against COVID-19 have not yet been determined. "Even though levels of neutralizing antibody production declined, the stable T-cell response and non-neutralizing antibody performance at month 8 may explain why vaccines continue to provide meaningful protection against severe COVID-19," notes lead study author I-Rees Collier.