The United States is currently facing three main variant threats, according to the Centers for Disease Control and Prevention: B.1.1.7, which originated in the United Kingdom; B.1.351 from South Africa; and the P.1 variant, which originated in Brazil.
Acting FDA Commissioner Janet Woodcock, MD, said on a telephone press briefing call Feb. 22 that the FDA has already been communicating with individual manufacturers as they assess the variants’ effect on their products, but these guidelines are issued for the sake of transparency and to welcome scientific input.
Tailoring may be necessary
Dr. Woodcock emphasized that, “at this time, available data suggest the FDA-authorized vaccines are effective in protecting circulating strains of SARS-CoV-2.” However, in the event the strains start to show resistance, it may be necessary to tailor the vaccine to the variant.
In that case, effectiveness of a modified vaccine should be determined by data from clinical immunogenicity studies, which would compare a recipient’s immune response with virus variants induced by the modified vaccine against the immune response to the authorized vaccine, the guidance states.
Manufacturers should also study the vaccine in both nonvaccinated people and people fully vaccinated with the authorized vaccine, according to the guidance.
Peter Marks, MD, PhD, director of the FDA’s Center for Biologics Evaluation and Research, said on the call that the clinical immunogenicity data is needed to understand, for instance, whether a new vaccine strain is able to cover the new and old strain or whether it just covers the new strain. Information is also needed to understand whether the modified vaccine, when given to someone fully vaccinated, will still promote a positive response without introducing safety concerns.
Further discussions will be necessary to decide whether future modified vaccines may be authorized without the need for clinical studies.
Variants and testing
The FDA’s updated guidance for test developers, Policy for Evaluating Impact of Viral Mutations on COVID-19 Tests, includes information that test performance can be influenced by the sequence of the variant, prevalence of the variant in the population, or design of the test. For example, molecular tests designed to detect multiple SARS-CoV-2 genetic targets are less susceptible to genetic variants than tests designed to detect a single genetic target.
The FDA already issued a safety alert on Jan. 8 to caution that genetic mutations to the virus in a patient sample can potentially change the performance of a diagnostic test. The FDA identified three tests that had been granted emergency-use authorization (EUA) that are known to be affected.
However, Dr. Woodcock said on the call, “at this time the impact does not appear to be significant.”
Updated guidance for therapeutics
The FDA has issued new guidance on the effect of variants on monoclonal antibody treatments.
“The FDA is aware that some of the monoclonal antibodies that have been authorized are less active against some of the SARS-CoV-2 variants that have emerged,” the FDA noted in its press release. “This guidance provides recommendations on efficient approaches to the generation of ... manufacturing and controls data that could potentially support an EUA for monoclonal antibody products that may be effective against emerging variants.”
While the FDA is monitoring the effects of variants, manufacturers bear a lot of the responsibility as well.
The FDA added: “With these guidances, the FDA is encouraging developers of drugs or biological products targeting SARS-CoV-2 to continuously monitor genomic databases for emerging SARS-CoV-2 variants and evaluate phenotypically any specific variants in the product target that are becoming prevalent or could potentially impact its activity.”
Dr.Woodcock added that “we urge all Americans to continue to get tested, get their vaccines when available, and follow important heath measures such as handwashing, masking, and social distancing.”
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