Antibodies in first vaccine limit efficacy of booster doses, study finds
The first COVID-19 vaccine induces potent antibodies that protect against SARS-CoV-2. However, a study from Northwestern Medicine (USA) has shown that. antibodies generated by that vaccination or previous infection may ‘impair’ booster vaccines.
This is because these antibodies ‘absorb’ the booster dose rapidly, before it has a chance to stimulate immune system cells, according to their findings, published in the scientific journal ‘Cell Reports’.
“Those same antibodies that protect against the virus also clear the vaccine very quickly. They think the vaccine is the virus.“, explained Pablo Peñaloza-MacMaster, lead author of the study, which was conducted in both humans and mice.
The researcher clarifies, in any case, that having antibodies and receiving a booster dose “is a good thing, so anyone who should receive their booster vaccine should do so.” “We don’t want people to think otherwise. The study only points to possible strategies by which new-generation vaccines could be adjusted to improve their efficacy, e.g.by developing vaccines that avoid preexisting antibodies.“, Peñaloza-MacMaster points out.
In a cohort of 85 people who had been vaccinated with either the Moderna or Pfizer-BioNTech vaccines, scientists found that lower antibody levels before a booster dose were associated with higher antibody levels after the booster.
“This suggests that pre-existing antibodies induced by previous vaccinations. May adversely affect the level of responses induced by booster vaccines. mRNA booster vaccines,” the researcher emphasized.
Subsequent studies in mice showed that antibodies generated by earlier vaccinations accelerated the elimination of the vaccine from the body.limiting the amount of vaccine available to trigger new immune responses after the booster vaccination.
“In other words, the antibody responses generated after previous vaccinations. rapidly eliminate the vaccine during a subsequent booster vaccination, limiting the immune response that can be generated by the booster vaccine,” Peñaloza-MacMaster detailed.
This is not simply due to competition between antibodies and B cells for the vaccine antigen, but appears to be the result of the so-called ‘antibody effector mechanisms’ that eliminate foreign substances from the organism.
In experiments with mice, scientists discovered that vaccines adapted to omicron are superior to the original vaccines in eliminating infection with this variant if the animal’s immune system has never encountered the original SARS-CoV-2 through vaccination. But the superiority of the omicron-adapted vaccine is more limited if the animal has already received the original vaccine.
Increasing the time between vaccinations.
According to Penaloza-MacMaster, these new results also suggest why increasing the time between vaccinations is beneficial to the immune response.
In earlier studies, these researchers already demonstrated that. the longer the interval between vaccinations, the better the response.. “It is better to wait six months than two weeks before boostering, but the reasons were not clear. We thought it might simply be due to time-dependent maturation of the immune response. But another reason is that the decrease in antibodies would allow the booster dose to persist in the body longer. If the booster injection into the muscle lasts longer, robust immune responses are likely to develop,” the scientist noted.
Since the experiments in this work show that high levels of antibodies induced by previous vaccines or infections can be detrimental to vaccine boosters, scientists plan further experiments to administer drugs that transiently block antibody activity. They plan to administer these drugs at the time of the booster so that immune cells will better perceive the vaccine.
“Although antibody responses are an essential component of the immune system, our data suggest that a very transient blockade of these responses during vaccination (only for a few hours) could have a profound beneficial effect on mRNA vaccines,” Peñaloza-MacMaster reiterated.