Impact of the Covid-19 Pandemic on Flu Vaccines: Evolution Ahead
With the Covid-19 pandemic reshaping health priorities, the elimination of a flu strain has significant implications on future vaccines. For a decade, flu shots in the U.S. shielded against four virus strains, ensuring protection from two A strains and two B strains.
For the past decade, Americans have been able to get flu shots that guard against four types of the virus: two A strains and two B strains.
But this upcoming fall, all flu shots given out in the United States will likely only have three strains, and this adjustment is due to the impact of Covid-19.
In 2020, the precautions taken to prevent Covid-19 had an unexpected positive outcome. The Yamagata clade, a branch of the flu virus, vanished and has not been seen since.
Each year, the flu shot usually includes a Yamagata strain. Vaccine makers now had to decide whether to remove this strain from the formula or keep it, considering that B-viruses can be tricky.
In the 1990s, Yamagata was thriving, and another type of flu virus, Victoria, was rarely detected in testing. However, it made a comeback in the 2000s. What if Yamagata resurfaced after being inactive for a long time? Changing the way flu vaccines are made isn't a simple or fast process. These changes need to go through regulatory review and approval.
Bianca Perez, nurse practitioner at CVS Minute Clinic in Miramar, Florida, administers a flu vaccine to Giselle Castillo-Righton of Miramar on Wednesday, Aug. 30, 2023. (Carline Jean/South Florida Sun Sentinel/Tribune News Service via Getty Images)
Bianca Perez, a nurse practitioner at CVS Minute Clinic in Miramar, Florida, gave a flu vaccine to Giselle Castillo-Righton from Miramar on Wednesday, Aug. 30, 2023. (Carline Jean/South Florida Sun Sentinel/Tribune News Service via Getty Images)
The image was captured by Carline Jean from the South Florida Sun Sentinel.
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In September, the World Health Organization announced that including Yamagata-lineage antigens in flu vaccines is no longer necessary. Following this, vaccine experts advising the US Food and Drug Administration recommended dropping the Yamagata strains promptly.
Dr. Paul Offit, director of the Vaccine Education Center at Children’s Hospital of Philadelphia and a member of the FDA's Vaccines and Biological Products Advisory Committee (VRBPAC), mentioned that discussions about this decision have been ongoing for four years.
The committee will meet on Tuesday to talk about what to do next and decide on the flu vaccine recommendations for the upcoming autumn season.
Offit mentioned that he anticipates all flu vaccines in the US this fall will be three-strain vaccines, containing two A strains and a B/Victoria strain. However, there will be no B/Yamagata strain included, following the suggestions from the WHO and VRBPAC.
There are good reasons for dropping the Yamagata strain, Offit said.
“You don’t want to be vaccinating people for something they don’t need,” he said.
Dr. Jodie Guest, senior vice chair of the Department of Epidemiology at Emory University’s Rollins School of Public Health, also pointed out the potential harms of continuing to include it.
According to Dr. Guest, flu vaccines are produced using live or attenuated virus, which must be grown in a lab. This process increases the risk of the virus escaping from the lab.
"While the risk is very small, there is a chance that reintroducing it into the population could happen through a vaccine," Guest explained.
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Some experts suggest that removing the Yamagata strain could help boost production capacity, allowing for more doses to be made worldwide. This could be especially helpful for countries facing shortages.
In an article published on February 28 in the New England Journal of Medicine, Dr. Arnold Monto, Dr. Maria Zambon, and Dr. Jerry Weir discussed the expected changes in vaccines. They are FDA vaccine advisers and experts from the UK Health Security Agency.
The experts mentioned that the current vaccine formulas could be improved. They suggested potentially doubling the dose or adding a second member from the same family for the A/H3N2 component. This is because the B/Victoria and A/H1N1 strains in the vaccine are usually more effective.
However, the authors mention that implementing this change would involve testing and regulatory approval. Therefore, the return of four-strain flu shots is not expected in the near future. They suggest that it will be a long-term goal to enhance vaccine effectiveness.
Editor's P/S:
The adjustment to the flu shot formula, removing the Yamagata strain, is a testament to the evolving nature of viruses and the importance of scientific research. The fact that the Yamagata strain has not been detected since 2020 highlights the unpredictable nature of viruses and the need for ongoing surveillance. The decision to exclude it from the upcoming flu shot is a cautious and responsible one, prioritizing the safety and effectiveness of the vaccine.
While the removal of the Yamagata strain may raise concerns about its potential resurgence, the experts involved have carefully considered the risks and benefits. The potential harm of including an unnecessary strain in the vaccine, such as the risk of escape from the lab, outweighs the benefits. The focus on optimizing vaccine effectiveness and ensuring a sufficient supply for global distribution is crucial. The article emphasizes the complexities of vaccine development and the ongoing need for research and collaboration to improve vaccine efficacy and safety.
