Flu virus samples submitted by patients globally serve to inform understanding of viral evolution and guide the World Health Organization's (WHO) annual flu vaccine design. Reports indicate a significant reduction in these submissions this year, which may affect the effectiveness of future flu vaccines.
Reduced Sample Collection
Demetre Daskalakis, former head of the National Center for Immunization and Respiratory Diseases at the U.S. Centers for Disease Control and Prevention (CDC) until August, stated that the flow of this data had substantially decreased. From February through July, the CDC received 427 samples, marking a 60% reduction compared to the same period in the previous year. Only 12 countries had submitted samples to the CDC by July, a 65% decrease from 2024 figures. The CDC did not respond to inquiries regarding these statistics.
Daniel Jernigan, who also resigned from his role as director of the CDC's National Center for Emerging and Zoonotic Infectious Diseases in August, commented that a reduction in incoming virus samples impacts vaccine composition, potentially leading to decreased vaccine effectiveness.
Global Network Impact
A network of seven WHO collaborating centers, including the CDC, processes virus samples from over 150 National Influenza Centers worldwide. Maria Van Kerkhove, interim director of the WHO's department of epidemic and pandemic threat management, reported a decrease in sample shipments to this global network this year.
The WHO typically funds the shipment of these samples. However, on January 20, President Trump announced the U.S. withdrawal from the organization, citing accusations of Chinese control. This action resulted in an approximate billion-dollar reduction in the WHO's budget, leading to a decrease in funds allocated for sample shipments. Ms. Van Kerkhove stated the WHO is seeking alternative funding to maintain its flu monitoring and assessment capabilities independently of any single member state.
Kanta Subbarao, a flu researcher at Laval University and former head of a collaborating center, indicated that a sustained reduction in sample submissions could result in a less complete understanding of influenza evolution. She further stated that a decrease in national influenza centers' ability to share samples would significantly impact influenza surveillance.
Implications for Vaccine Development
Annually in February and September, scientists from WHO collaborating centers convene to determine the influenza strains for the upcoming northern and southern hemisphere flu seasons. Subbarao noted that flu vaccines typically include multiple strains to provide protection, as the dominant virus for the next season cannot be precisely predicted.
The selection of vaccine strains involves predictive analysis, which is informed by the work of specialized laboratories such as the CDC. Daskalakis described the CDC's process as involving viral analysis, sequencing, and ferret testing to assess pandemic potential and predict circulating strains. Arnold Monto, an epidemiologist at the University of Michigan, stated that reduced sample numbers would complicate these analyses by decreasing the available data for decision-making.
WHO officials did not specify the exact reduction in data shared with collaborating centers. The next meeting for strain selection is in February, allowing time for additional sample submissions. Daskalakis expressed concern that the CDC's reduced sample intake might be difficult to reverse, potentially due to countries' reluctance to share data with the U.S. following its WHO withdrawal.
Pandemic Preparedness Concerns
Daskalakis indicated that reduced CDC involvement could diminish U.S. pandemic preparedness. He noted that the CDC usually receives approximately a dozen candidate vaccine viruses from the WHO network for vaccine production, in addition to thousands of influenza samples. By late August, the CDC had received two such viruses, according to Daskalakis, which could affect the ability to scale up a response to a potential flu pandemic.
Daskalakis also stated that the CDC's insight into other pathogens, including COVID-19 and polio, is decreasing, which may hinder the agency's ability to identify new viral variants that could lead to outbreaks. He explained that the surveillance system's effectiveness in identifying concerning elements relies on sufficient data input; insufficient data would prolong identification efforts. Daskalakis previously observed during the COVID-19 pandemic that delays and reduced coordination had direct impacts on mortality. He predicted similar outcomes if the U.S. remains isolated during a future viral event.