The lab study evaluated and compared the strength of antibody response in people who were fully vaccinated with the Pfizer vaccine and in people who received a Pfizer booster after one month and four months, respectively.
Researchers found that for people who received two Pfizer doses, the antibody titer levels against Omicron were low, but a booster shot restored the antibody response. Four months after a booster, the titer levels had declined but remained more protective against the variant than only having two doses.
Experts are unsure how long the booster protection will persist after the four month mark, but continue to express confidence in the vaccine’s ability to prevent severe illness and death.
“The current vaccine is good for prevention of severe disease, hospitalization, and death,” Pei-Yong Shi, PhD, distinguished chair in innovations in molecular biology at the University of Texas Medical Branch and senior author of the study, wrote in an email to Verywell. “We know two and three doses would not efficiently prevent infection as we wish for.”
Real-World Data on Booster Effectiveness Against Omicron
Data from the Centers for Disease Control and Prevention (CDC) shows that mRNA boosters are highly effective at preventing COVID-19 hospitalizations and deaths during the Omicron surge. Despite alarming increases in positive cases, hospitalization and death rates have remained lower in people who were vaccinated and boosted.
In a recent study, the agency found that when the Delta variant was the dominant strain in circulation, a third dose of mRNA COVID-19 vaccine was 94% effective both at preventing hospitalizations and COVID-19–related emergency care visits. Two doses, with no booster, were 86% effective at preventing emergency visits within 14–179 days after vaccination and 76% effective 180 days or more days after vaccination.
The agency had less data on people in the Omicron-dominant period but drew similar conclusions on booster effectiveness. According to the CDC findings, a third dose of an mRNA COVID-19 vaccine was 90% effective at preventing hospitalization and 82% effective at preventing emergency care visits.
Two doses were 81% effective at preventing hospitalization within 14–179 days after vaccination and 57% effective 180 or more days after vaccination. They were 52% effective at preventing emergency visits within 14–179 days after vaccination and only 38% effective 180 or more days after vaccination.
The study did not evaluate children or patients who had been vaccinated with the Johnson & Johnson vaccine. The findings show a decrease in vaccine efficacy with time and highlights the importance of vaccines and booster shots, the researchers concluded.
Another recent study from the CDC looked at booster effectiveness against both infection and death in comparison to two doses.
During October and November 2021, the agency found that unvaccinated people had nearly 14 times the risk of COVID-19 infection and more than 50 times the risk of death when compared with fully vaccinated people who had a booster. People who had received two doses of vaccine had about 3.5 times the risk of infection than people who were boosted and about six times the risk of COVID-19 death.
Will There Be a Second Booster?
More research is needed to determine how long the booster’s protection will persist after four months, and these findings will be crucial for helping to guide decisions about whether or not to authorize a fourth vaccine dose, Shi wrote.
Preliminary data from Israel suggests that a fourth vaccine dose only slightly increases antibodies and may not significantly impact protection levels, particularly against Omicron.
Further research on booster durability will also be necessary for assessing the need—or lack thereof—for an Omicron-specific vaccine, which Shi referred to as “backup."
“We have to pursue both vaccine approaches,” he said.
The information in this article is current as of the date listed, which means newer information may be available when you read this. For the most recent updates on COVID-19, visit our coronavirus news page.
