The authors of the new study said that while the boosters are important and necessary to fight off COVID-19 and its various strains, getting the boosters too soon limited their efficacy.
The study was published Tuesday in the latest edition of the medical journal Cell Reports.
Authors of the new study said antibodies from the original vaccine at times attack the boosters as a matter of mistaken identity before the boosters can stimulate the cells from the immune system.
The researchers said they found the same result in humans and mice.
"Those same antibodies that protect you against the virus also clear the vaccine very fast," Pablo Penaloza-MacMaster, the lead author of the study, said in a statement. "They think the vaccine is the virus.
"It is important to clarify that having antibodies and getting boosted is a good thing, so anyone who is due their booster shots should do so. We don't want people to think otherwise."
Penaloza-MacMaster, assistant professor of microbiology-immunology at Northwestern University Feinberg School of Medicine, said the lessons from the research will help in future studies.
"The study just pinpoints potential strategies by which next-generation vaccines could be tweaked to improve their efficacy, for example, by developing vaccines that bypass pre-existing antibodies," Penaloza-MacMaster said.
Researchers said in a cohort of 85 people who had been vaccinated with the Moderna or Pfizer-BioNTech vaccines, scientists learned that lower antibody levels before a booster were associated with a higher-fold increase in antibody levels after the booster.
"This suggests that pre-existing antibodies induced by prior vaccinations may negatively affect the level of responses induced by mRNA booster vaccines," Penaloza-MacMaster said.
He said in experiments in mice, scientists found the updated Omicron vaccines were superior to the original vaccines, clearing the Omicron infection if the animal's immune system has never "seen" the original coronavirus through vaccination before.
It found, though, the relative superiority of an Omicron vaccine was more limited if the animal had already had the original vaccine.
The research made the case for longer times between vaccinations, which the study suggest improves the effectiveness of the booster.
"It's better to wait six months than two weeks before you boost, but the reasons for this were not clear," he said. "We have thought this could be simply due to the time-dependent maturation of the immune response.
"But another reason is that the waning of antibodies would allow the booster to persist in the body for a longer time. If the booster shot in your muscle perdures for a longer time, you are likely to develop robust immune responses."
Mixed results for Moderna mRNA flu vaccine trial
Washington (AFP) Feb 16, 2023 -
US biotech company Moderna said Thursday it had mixed results from a large-scale trial of its mRNA flu shot, based on the same technology used in its successful Covid-19 vaccine.
Moderna's experimental mRNA-1010 flu shot is "quadrivalent," meaning it targets four strains of flu: A/H1N1, A/H3N2, B/Yamagata and B/Victoria -- selected based on recommendations by the World Health Organization (WHO).
The Massachusetts-based company said that its flu shot generated an immune response against influenza A strains that was equal or superior to that of already licensed vaccines.
However, it fell short of the already approved vaccines against strains of the less-common influenza B, Moderna said in a statement.
"Today's results represent an important step forward in the development of mRNA-based influenza vaccines," Moderna president Stephen Hoge said.
"We have already updated the vaccine that we believe could improve immune responses against influenza B and will seek to quickly confirm those improvements in an upcoming clinical study."
The Phase 3 trial of the mRNA shot involved 6,102 adults in Argentina, Australia, Colombia, Panama, and the Philippines during the Southern Hemisphere influenza season.
Participants received a single dose of mRNA-1010 or a single dose of a licensed influenza vaccine.
Moderna said 70 percent of the mRNA-1010 recipients reported adverse reactions such as headaches, swelling and fatigue compared to 48 percent in the other group.
Virus strains have to be selected six to nine months before the vaccines are intended to be used, and their efficacy is approximately 40 to 60 percent.
Moderna is simultaneously conducting an efficacy trial of its vaccine.
Moderna and other vaccine manufacturers, including Sanofi, hope that mRNA technology -- which provokes an immune response by delivering genetic molecules containing the code for key parts of a pathogen into human cells -- can accelerate immunization development and production, and heighten efficacy.
There are some three to five million severe influenza cases annually worldwide and between 290,000 and 650,000 deaths, the WHO says.
Moderna's stock price was down more than six percent in after-hours trading in New York.
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