Pfizer and BioNTech said in a press release that people who received their bivalent booster shots had far higher levels of antibodies to fight SARS-CoV-2, than people who received previous booster shots.
The companies announced the findings from phase 2/3 studies, but those findings were not yet peer-reviewed.
Bivalent COVID-19 boosters that target both the original form of the coronavirus and the currently circulating BA.4 and BA.5 Omicron variants are now available in the United States for people as young as 5 years of age.
The Food and Drug Administration authorized these bivalent COVID-19 boosters on Aug. 31 for people 12 years and olderTrusted Source, and on Oct. 12 for younger age groupsTrusted Source.
New data finds bivalent boosters may result in more protection, especially for people over 55
According to the data published by Pfizer and BioNTech, in people over age 55 the bivalent booster shot was linked to an over 13-fold increase in antibody levels compared to pre-booster levels.
The traditional monovalent booster shots led to a 2.9 fold increase in antibody levels in people over age 55 compared to pre-booster levels.
The bivalent shot was found to lead to a 9.5 fold increase in antibody levels for adults aged 18 to 55, compared to pre-booster levels.
“These data demonstrate that our BA.4/BA.5-adapted bivalent vaccine works as conceptually planned in providing stronger protection against the Omicron BA.4 and BA.5 sublineages,” Dr. Ugur Sahin, CEO and Co-founder of BioNTech said in the statement. “In the next step and as part of our science-based approach we will continue to evaluate the cross-neutralization of the adapted vaccine against new variants and sublineages. Our goal is to provide broader immunity against COVID-19 caused by SARS-CoV-2, including Omicron and other circulating strains.”
New bivalent boosters found safe
The new data from Pfizer and BioNTech comes one day after a study from the U.S. Centers for Disease Control and Prevention found that the new bivalent boosters had a similar safety profileTrusted Source as previous COVID-19 vaccines.
In an effort to get ahead of the rapidly-changing coronavirus, the U.S. Food and Drug Administration authorized these bivalent boosters before data from clinical trials in people was available.
Since the FDA’s initial authorization of the bivalent vaccines, several new coronavirus subvariants have emerged around the world. Dr. Ashish Jha, head of the White House COVID task force, said Oct. 11 during a press briefing that the administration is “carefully monitoring” these strains, including “ones that evade some of our treatments.”
However, because these subvariants all arose from existing Omicron strains, the “updated bivalent vaccines should provide a much higher degree of protection than the original prototype vaccine would have,” said Jha.
The FDA said in a statement in August that it based its decision for the bivalent vaccines on the “totality of available evidence.”
This includes animal studies on the BA.4/5 boosters, clinical trials of bivalent BA.1 boosters, clinical trials of the original vaccines and boosters, and ongoing monitoring of the safety of the current vaccines.
In authorizing the bivalent vaccines for younger age groups, the agency based its decision on the same evidence.
Experts told Healthline that — given this evidence and the fact that the BA.4/5 bivalent boosters are so similar to the BA.1 boosters — there’s no question that the newly authorized bivalent vaccines are safe.
However, it may take some time before we know how much of an immune boost the updated vaccines will offer against the currently circulating Omicron variants — and even longer to know how well they stand up to future variants that may arise.
Long track record of safety
Dr. Mohammad Sobhanie, an infectious disease physician at The Ohio State University Wexner Medical Center in Columbus, Ohio, pointed out that Moderna and Pfizer-BioNTech used the exact same technology to develop the BA.4/5 bivalent boosters as they did their original COVID-19 vaccines, as well as the BA.1 bivalent boosters.
He compared this change to how the seasonal flu vaccines are updated each year to match the influenza strains that are expected to be in circulation. Unless vaccine makers use new technology to produce the flu vaccines, no additional clinical trials are needed.
With the COVID-19 vaccines, there is already a long track record of safety that can be used to support the safety of the BA.4/5 bivalent vaccines.
In the United States alone, over 640 million doses of the mRNA COVID-19 vaccines have been given, including over 26.3 million doses of the bivalent vaccines, according to the CDC
In addition, “there’s nothing dramatically new that’s in the [BA.4/5 bivalent] vaccine, other than that they’ve changed what it’s targeting,” said Sobhanie. “So the safety profile should be similar to that of the original vaccines.”
This vaccine target is the spike protein of the coronavirus, which the virus uses to infect cells. The spike protein of the Omicron and other variants differ from that of the original form of the virus, on which the first vaccines were based.
David R. Martinez, PhD, a viral immunologist at the UNC Gillings School of Global Public Health in Chapel Hill, North Carolina, said the spike proteins of the BA.1, BA.4 and BA.5 variants — which are all versions of Omicron — are very similar.
As a result, “I think we have enough information to be able to determine that the [BA.4/5 bivalent] vaccine is safe,” he said, because “BA.4 and BA.5 have relatively few differences in the spike protein compared to BA.1, which did undergo testing in humans.”
Clinical trials of the Moderna and Pfizer-BioNTech bivalent BA.1 boosters did not identify any new safety concerns, the FDA said in its statement.
The most commonly reported side effects were similar to the original vaccines and boosters, such as pain, redness and swelling at the injection site, fatigue, headache, muscle pain, chills, joint pain, and fever.
These trials also showed that the BA.1 bivalent vaccine generated a stronger immune response against that variant, compared to the original vaccine, the FDA said.
The clinical trial for the BA.1 bivalent booster was smaller than the trials for the original vaccine, so a rare side effect may not show up.
However, “even if you performed a large clinical trial, you may not always pick up every rare side effect,” said Martinez. “So we continue to monitor the vaccines in real time after they are authorized.”
This routine monitoring is how the FDA and CDC identified the increased risk of heart inflammation — myocarditis and pericarditis — which was not detected in the original clinical trials.
This side effect generally occurs within the first week after receipt of the second dose or first booster of the original mRNA COVID-19 vaccines.
For the Moderna COVID-19 vaccineTrusted Source, the risk of myocarditis or pericarditis is highest in males 18 through 24 years of age. For the Pfizer-BioNTech vaccineTrusted Source, the risk is highest in males 12 through 17 years of age.
The FDA has included this risk on the fact sheets for the updated bivalent vaccines, the agency said.
Scientists monitor vaccine effects
Even with the FDA authorizing updated vaccines, data show that the original vaccines continue to provide strong protection against severe illness, especially when people have received both the primary series and at least one booster.
“The current vaccines are still holding up,” said Sobhanie. However, “if these updated boosters can prevent more [COVID-19] hospital admissions and deaths, that’s definitely a plus.”
With the bivalent BA.4/5 booster, the United States has a chance to roll out a vaccine that matches the currently circulating version of the virus.
“Hopefully, if you can get vaccinated against these [BA.4 and BA.5], then it should provide protection against infection,” said Sobhanie. “This is something that is pretty useful as we head into the fall and winter months, when people are more likely to gather indoors.”
The inclusion of the original formulation of the vaccine in the booster provides a hedge against a variant similar to the original strain arising.
However, scientists don’t know for certain how much protection the updated boosters will offer.
Figuring this out in advance is complicated by the complex mix of immunity Americans have gained through vaccination and infection with different variants, including multiple infections for some people. This prior immunity may affect a person’s response to vaccination with an updated booster.
“We are hoping that having a vaccine closer-matched to the circulating variants will have an impact on the transmission of the virus,” said Martinez. However, “even though it’s reasonable to think this, we really don’t know if it will actually do that.”
While some experts question the benefits of the updated boosters for younger, healthy people, Martinez said there are certain people who will definitely benefit from the bivalent vaccines.
“Where this vaccine could probably offer the most advantage would be in elderly individuals who have waning immunity,” he said, “and potentially in reducing the transmission of BA.5, assuming it’s still circulating in two months from now.”