In a meeting yesterday to discuss the strains to include in flu vaccines for the 2024-25 flu season, a federal vaccine advisory group urged manufacturers of vaccines for the US market to drop the influenza B Yamagata lineage strain.

The Food and Drug Administration (FDA) Vaccines and Related Biological Products Advisory Committee (VRBPAC) in an announcement following the meeting noted that the Yamagata influenza B lineage hasn't been detected since March 2020, and evidence suggests it no longer poses a public health threat.

Move is part of broader push for return to trivalent formulations

Yesterday's vote on a return to trivalent (three-strain) vaccines follows its discussions in October 2023 about whether quadrivalent (four-strain) vaccines were still needed. In September 2023, the World Health Organization (WHO) flu vaccine advisers recommended a switch back to trivalent flu vaccines.

The FDA said it has been working with manufacturers to move to trivalent formulations for the upcoming flu season. "FDA anticipates that there will be an adequate and diverse supply of approved trivalent seasonal influenza vaccines for the United States in the coming season," it said.

FDA anticipates that there will be an adequate and diverse supply of approved trivalent seasonal influenza vaccines.

However, it also acknowledged that not all countries can revert to trivalent vaccines as fast as the United States is moving and that companies that have existing FDA-approved flu vaccines and want to export them can include the Yamagata influenza B strain.

VRBPAC also approved the strains to include in the 2024-25 trivalent vaccines, which align with the ones recommended for the upcoming Northern Hemisphere season by the World Health Organization for both egg- and cell-based vaccines.

A new analysis of all-cause mortality of Hispanic and Latino adults published in Annals of Internal Medicine shows Mexicans and Central Americans were most affected by the pandemic.

The study was based on trends seen among 15,568 adults aged 18 to 74 years who participated in the HCHS/SOL (Hispanic Community Health Study/Study of Latinos). Baseline mortality trends from 2008 through 2011 were compared to trends seen in 2020 and 2021.

Participants were recruited from the Bronx, New York City; Chicago; Miami; and San Diego and were of Central American, Cuban, Dominican, Mexican, Puerto Rican, and South American backgrounds.

Socioeconomic factors at play during pandemic

Prior to the pandemic, cumulative mortality risks were higher in the Puerto Rican and Cuban groups (6.3% and 5.9%, respectively) and lowest in the South American group (2.3%). Mortality was higher among those born in the United States and lower among immigrants, and the increased mortality risk among Puerto Ricans and Cubans was most often associated with lifestyle factors, including diet.

"During the pandemic, marginal 2-year cumulative mortality risks adjusted for age ranged from 1.1% (South American) to 2.0% (Central American), and CIs [confidence intervals] overlapped across all groups," the authors wrote. "Our findings (based on 2 years of follow-up) suggest that mortality risks varied during the pandemic after adjustment for lifestyle and clinical factors—that is, risks were somewhat higher for persons of Central American and Mexican backgrounds than for those of Puerto Rican and Cuban backgrounds."

Risks were somewhat higher for persons of Central American and Mexican backgrounds than for those of Puerto Rican and Cuban backgrounds

Lifestyle factors were second to socioeconomic factors in contributing to mortality, the authors wrote, as the pandemic emphasized discrepancies among Latino groups. For example, according to the 2020 census, 20.3% of Mexican Latinos had no insurance, compared with 8% of Puerto Rican Latinos.

In an editorial on the study, authors write the HCHS/SOL, "holds great promise for the further development of theoretical models and frameworks on Latino mortality and health," an area of study missing in US public health research.

The tetanus and diphtheria (Td) vaccine is expected to be in short supply throughout the year after one of the two suppliers to the United States discontinued production, the Centers for Disease Control and Prevention (CDC) warns.

The nonprofit organization MassBiologics recently stopped production of its TdVax vaccine, leaving only Sanofi's Tenivac on the market. Grifols USA, which distributes TdVax, told the CDC that supplies are expected to last only until June, and Sanofi has said that it's working to augment US supplies of Tenivac to try to offset the gap.

To conserve available supplies of Tenivac, the CDC has implemented temporary ordering limits. While supplies of the diphtheria, tetanus, and pertussis (Tdap) vaccines (Sanofi's Adacel and GSK's Boostrix) aren't limited, they are more expensive, and a very small fraction of patients can develop encephalopathy (brain damage) from the pertussis component.

Tdap vaccine can be substituted in most people

The CDC recommends that healthcare providers use Tdap vaccine rather than Td vaccine in patients without a pertussis vaccine contraindication. It said that Tdap can also be substituted when a tetanus booster is needed for wound management. Td and Tdap vaccines are given during childhood and then every 10 years or when needed for tetanus prevention after severe or contaminated wounds or burns.

While supplies of the diphtheria, tetanus, and pertussis (Tdap) vaccines aren't limited, they are more expensive, and a very small fraction of patients can develop encephalopathy (brain damage) from the pertussis component.

Also known as lockjaw, tetanus is a very rare infection caused by the bacterium Clostridium tetani, which releases a toxin that causes painful muscle spasms. Diphtheria, caused by the toxin-releasing bacterium Corynebacterium diphtheriae, can cause shortness of breath, abnormal heart rhythms, and death. Pertussis, also known as whooping cough, is a highly contagious infection of the respiratory tract caused by Bordetella pertussis or Bordetella parapertussis bacteria.

The Td vaccine shortage comes on the heels of a recent and ongoing US shortage of the new respiratory syncytial virus (RSV) monoclonal antibody injection for infants, Beyfortus.