One volunteer was given a vaccine injection when he participated in a coronavirus disease (COVID-19) vaccination study on September 24, 2020 at a research center in Hollywood, Florida, USA.
Marco Bello | Reuters
According to a top official from the drug regulator, the FDA may decide by early summer whether vaccine manufacturers will need to change existing covid shots to target different virus variants to avoid another potential increase this fall.
Dr. Peter Marks, who heads the FDA office responsible for vaccine safety and efficacy, told the drug regulatory advisory committee on Wednesday that a decision needed to be made by June to make the shots available in the fall. Marx said the United States could face another wave of infection at that time because the virus would continue to evolve as immunity from existing vaccines decreased.
Robert Johnson, a senior official at the Biomedical Advanced Research and Development Authority, told the meeting that the biggest challenge in updating shots would be to coordinate among vaccine manufacturers to make sure they are focusing on the correct Covid variants.
Pfizer, Moderna and other vaccine manufacturers are conducting clinical trials on Omicron-based shots. However, companies are not currently coordinating their new vaccine formulas, according to Jerry Weir, head of the FDA division of viral products. Several members of the FDA advisory panel have said that public health authorities need to develop a unified approach among vaccine manufacturers, such as updating the flu vaccine to target new strains each year.
Dr. Paul Offit, a member of the FDA committee, said the CDC would have to take the lead in deciding whether vaccines would no longer be effective against serious illness, so the FDA and the National Institutes of Health could then work with the agencies to determine the best course of action. Forward to a new shot.
“At some level, companies point the conversation here,” Afit said. “You often hear that companies now have an Omicron specific vaccine, or a vaccine they can now combine with the influenza vaccine. It shouldn’t come from them, it really should come from us.”
FDA officials have suggested using the process to develop a new flu vaccine as a guide to changing covid shots. Each year, the World Health Organization makes a recommendation about the composition of the flu vaccine. The FDA makes its own decisions based on the recommendations of its committee, which strain should be shot for the United States.
Uncertainty over the evolutionary trajectory of covid, in contrast to flu predictability, makes it difficult to determine how vaccines should be updated – or whether they require any changes at all.
According to CDC data presented at the meeting, three doses of the Pfizer or Modern vaccine were more than 80% effective in preventing hospitalization among healthy adults during omicon waves. But the companies’ vaccines are still based on the original version of the virus that originated in Wuhan, China, and their effectiveness against the infection has dropped significantly since the epidemic began.
According to Trevor Bedford, a virologist at the Fred Hutchinson Cancer Research Center, covid flu has changed two to 10 times faster, depending on the strain of the next virus. Bedford said he hopes the spike protein, which the covid virus uses to attack human cells, will continue to evolve. Vaccines target spikes and may reduce the effectiveness of shots as proteins change.
Bedford said the most likely scenario next year is that Omicron and its submarines will become more contagious and will further protect against vaccines and infections. However, he said it is difficult to predict whether another heavily transformed form associated with an epidemic response, such as Omicron, will occur in the winter.
“We don’t really know if these wild viruses will be a common feature, or a rare feature of local SARS-CoV-2 evolution,” Bedford said, using the scientific name of the virus that caused the covid.
Johnson noted that in the case of flu, vaccine manufacturers are able to create advance production plans based on a stable seasonal market. However, it is not yet clear whether covidia flu will follow a predictable seasonal pattern similar to that of flu, according to Dr. Kant Subbarao, a virologist who works with the flu for the World Health Organization.
FDA committee members say the central question of updating a vaccine is determining what metrics the public health authority should use to determine when shots have lost their effectiveness. According to Dr. Cody Meissner, an infectious disease specialist at Tufts University School of Medicine, scientists have not yet determined whether a specific antibody level produced by a vaccine translates to clear protection against the virus.
As a result, public health authorities will have to rely on hospital admissions rates to determine whether the vaccine is losing its effectiveness, Meissner said. However, it is also unclear whether the national hospital admissions data is primarily for patients admitted due to the virus, or for people who tested positive after admission for other reasons. Meissner points to data from Massachusetts showing that as of April 5, 65% of the 219 people hospitalized with covid were actually due to reasons other than the virus.
Dr Amanda Cohen, a CDC official, told the committee that repeated boosts were not a sustainable public health strategy. Cohen said the effectiveness of the vaccine against hospitalization remains high, and society may have to adopt a certain level of infection that can be treated with the antiviral pills now available on the market.
The FDA last week approved a fourth shot for adults 50 years of age or older without consulting the committee, a decision that has divided scientists and physicians, some of whom believe there is not enough data to support additional shots. Marx said the FDA did not consult with the committee because the drug regulator saw the approval as a way to provide additional protection for serious diseases until a broader decision is made for other populations.
“I think we’re on board too much and with the idea that we can’t encourage people like us to be as frequent as we are,” Marx told the committee. “I was the first to admit that this additional fourth booster dose that was approved was a stopgap measure until we got the things for a potential next booster given the emerging data,” Marks said.