Written by Timothy Huzar — Fact checked by Alexandra Sanfins, Ph.D.
In a new study, researchers have found that the antibodies that the body produces in response to the Pfizer-BioNTech COVID-19 vaccine reduce significantly in number in just 6 months.
The study, which has been accepted for publication in the Journal of Medical Biochemistry and is available as a preprint, also found that a person’s age or sex affected the number of antibodies they developed in response to the vaccine.
The research will contribute to debates about the use of booster vaccines for COVID-19 and whether they should be limited to specific “vulnerable” populations or rolled out universally.
One of the great achievements of the response to the COVID-19 pandemic is scientists’ rapid development of safe and effective vaccines.
Initial reports of more than 90% efficacy for many of the vaccines — including Pfizer-BioNTech — significantly exceeded many scientists’ hopes.
However, scientists know that immunity acquired through vaccination typically wanes over time.
In the context of the COVID-19 pandemic, understanding several related factors — including how long it takes for immunity to wane, how much it wanes by, and who is primarily affected — is important for deciding when to roll out booster jabs and to whom.
In the present study, the researchers looked at data from 787 healthcare workers aged 21–75 years in Verona, Italy.
The healthcare workers had received two doses of the Pfizer-BioNTech vaccine. The data included measurements of their SARS-CoV-2 antibody levels before their first vaccination, after their second vaccination, and then 1, 3, and 6 months after the second vaccination.
The researchers found that across age and sex, antibody levels reduced by more than 50% within 6 months of the second vaccination.
They also found that there were differences in the total antibody levels that participants had based on age and sex.
People under the age of 65 years had more than double the number of antibodies compared with people 65 years or older over the 6 months following the second vaccination. This followed a linear pattern as age reduced.
In addition, women had a higher number of antibodies than men, particularly if they were below the age of 65 years.
Dr. Brandon Michael Henry, a postdoctoral researcher at the Texas Biomedical Research Institute and co-leader of the study, says, “
hile we see how well vaccines have helped keep people out of the hospital and prevent life threatening disease, antibody levels are quickly declining in all persons regardless of age and sex.”
“Our study provides additional evidence that booster shots for all adults will be important to keep antibody levels up so we can continue to mount an effective immune response against [SARS-CoV-2] infection and prevent COVID-19 fatalities,” says Dr. Henry.
Dr. Henry suggests that the difference in antibody levels between men and women may be due to hormones. Men typically have more testosterone than women, and this hormone suppresses a person’s immune system. In contrast, estrogen — which is typically higher in women than in men — enhances the immune system.
Dr. Henry also wonders whether chromosomes could play a part. The X chromosome carries specific genes related to immunity, and females have two X chromosomes.
“Normally, only one X chromosome is active, and the other is mostly deactivated, but there is evidence that immune-related genes stay active on that redundant chromosome and help boost immune responses in women,” says Dr. Henry.
Immunity after infection?
Prof. Giuseppe Lippi, full professor of clinical biochemistry at the University of Verona and the corresponding author of the study, said to Medical News Today that he would expect a similar waning in immunity following a SARS-CoV-2 infection.
“Vaccination is a kind of ‘artificial’ infection. Therefore, antibody decline is predictably similar in people who recover from a SARS-CoV-2 infection as [it is] in vaccine recipients,” said Prof. Lippi.
Prof. Lippi also agreed that the findings suggest that booster shots will be necessary for everyone.
“Antibody decay is related to age and sex — higher in older males — but [it] displays a similar trend throughout all ages. Therefore, yes, booster doses of vaccines would be needed — sooner or later — for everybody,” said Prof. Lippi.
Speaking to MNT, Prof. Jeffrey Townsend — who is Elihu professor of biostatistics and professor of ecology and evolutionary biology at Yale School of Public Health, Connecticut, and was not involved in the study — agreed that the findings suggested booster vaccinations would be necessary. Prof. Townsend is corresponding author of a study in The Lancet Microbe on the durability of SARS-CoV-2 immunity.
“The decline in antibody levels with time following vaccination indicates a similarity between the waning of immunity to natural infection and the waning of immunity from vaccination and booster vaccination,” he said. “Other studies have demonstrated that both natural infection and vaccination are subject to decreasing efficacy in protection versus infection.”
“These results reinforce the need for booster vaccination for the prevention of infection by [SARS-CoV-2].”
– Prof. Townsend
Prof. Townsend also said that further research on waning SARS-CoV-2 immunity was necessary.
“Two aspects of research should be pursued. First, studies that better characterize the benefits of vaccination and booster vaccination for the prevention of symptomaticity, severe disease, and mortality.”
“And second, studies that quantitatively evaluate the relative roles of antibody waning and antigenic evolution of the virus in decreasing the benefits of natural infection, vaccination, and booster vaccination,” said Prof. Townsend.