In anticipation of another COVID-19 surge, the Food and Drug Administration (FDA) recently recommended vaccine makers to update their booster shots to include components of the Omicron subvariants BA.4 and BA.5.
Since flu-like illnesses tend to peak during the fall and winter, a potential COVID-19 wave drives the need for updated vaccine formulations, according to Mark Loafman, MD, MPH, a family physician at Cook County Health.
“The COVID mutations we are seeing now are different enough from the original virus to decrease the effectiveness of the vaccine's ability to prevent infection,” Loafman told Verywell.
Administering Omicron-adapted COVID-19 vaccines could expand immunity against circulating and emerging variants and maintain high protection against severe disease outcomes.
Prior to the FDA recommendation, Pfizer-BioNTech and Moderna had already released positive data on a bivalent vaccine, which contains antigens for both the Omicron variant and the original COVID-19 strain.
Based on reported data, the vaccines demonstrated slightly different levels of effectiveness against Omicron.
Only Moderna’s bivalent vaccine candidate (50 µg) has been tested specifically against Omicron BA.4 and BA.5, which showed a 5.4-fold increase in neutralizing antibodies, regardless of prior infection.
Pfizer's current bivalent vaccine candidates are also capable of neutralizing BA.4 and BA.5, but to a lesser degree than their effect on BA.1. The company said it will continue to collect more data to adapt its formulations to emerging sublineages if necessary.
“Given the fairly rapid mutations we are seeing with COVID, it is not surprising that the updated vaccine is one generation behind the newest variants circulating,” Loafman said.
Although the reformulations will be helpful, it's hard to predict how dominant BA.4 and BA.5 will be when the booster shots are available in the fall, said Perry N. Halkitis, PhD, dean of the Rutgers School of Public Health.
Halkitis said there is a false assumption that the original COVID-19 strain is no longer circulating now that BA.4 and BA.5 are the most prevalent versions of the virus. However, the updated vaccines will still be more effective since the current vaccines were developed two years ago, he added.
Both vaccine manufacturers shared their data with regulators in late June.
“They are under review now for emergency use authorization and appear to be on track for full FDA approval in the coming weeks, if not sooner, pending any new information that might affect that decision,” Loafman said.
Those at high risk of serious illness will likely be prioritized for the reformulated vaccines, he explained, but the general population may have access to the booster shots when more supply is in the works.
Halkitis said he recommends waiting to get a reformulated booster in the fall, as the current vaccines are "not going to address the current versions of the virus."
It is important to stay up to date with your COVID-19 vaccines, which includes getting the recommended booster shots when you are eligible. Pfizer and Moderna are developing Omicron-adapted boosters, but they are not expected to be widely available until the fall.
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