Immunity against the omicron coronavirus variant fades rapidly after a second and third dose of Pfizer and BioNTech’s Covid-19 vaccine, according to peer reviewed research published in JAMA Network Open on Friday, a finding that could support rolling out additional booster shots to vulnerable people as the variant drives an uptick in new cases across the country.
Levels of omicron-specific “neutralizing” antibodies–which can target the virus and stop it from replicating–decline rapidly after a second and third dose of Pfizer’s shot, according to the Danish study of 128 people who had received two or three doses.
Antibody levels are associated with protection from infection and disease and fell within weeks after receiving the shots, according to researchers. They were also lower than the level specific to the original or delta coronavirus variants.
Compared to original and delta variants, the proportion of omicron-specific antibodies detected in participants’ blood dropped “rapidly” from 76% four weeks after the second shot to 53% at weeks eight to 10 and 19% at weeks 12 to 14, the researchers found.
Omicron-specific antibody levels increased after the third dose–nearly 21-fold at week three and nearly 8-fold at week four, compared to four weeks after the second dose–and the shot generated a detectable response in most people for at least eight weeks, the researchers said.
However, antibody levels began to decline as soon as three weeks after booster shots. They fell 4.9-fold in the original variant and 5.6-fold in the delta. They also dropped 5.4-fold in the omicron, which was between weeks three through eight.
The “transient” antibody reaction after three doses of booster shots may be sufficient to fight the variant, especially among older adults, researchers stated.
Experts and regulators generally recognize the benefits of a third dose of vaccine to increase protection against serious illness or death. There is less consensus over whether additional shots are needed beyond that and questions over whether frequent boosting will be practical. While neutralizing antibodies are the main focus of vaccine research, they are also much more difficult to study. However, they are an important part of the immune system that protects us against disease. Other parts of the immune system, such as T cells, might be less effective at preventing infection but they are more durable than antibodies and can reduce the chance of serious illness if infected. Many experts believe this latter property is the primary function of vaccination, not preventing infection, and data shows they offer much more durable protection, including against omicron.