Vaccine Companies Say They ‘Stand Ready’ for Potential H5N1 Bird Flu Outbreak in Humans

Rescued chickens gather in an aviary at Farm Sanctuary’s Southern California Sanctuary in Acton, Calif., on Oct. 5, 2022. A wave of the highly pathogenic H5N1 avian flu has now entered Southern California as the fall bird migration sets in, raising concerns for wild birds and poultry farms in the region. Mario Tama/Getty Images

Some of the largest vaccine companies in the developed world are reportedly preparing avian flu H5N1 shots for humans in case the virus were to mutate and become easily transmissible from person to person.

Vaccine makers GSK, Moderna, and CSL Seqirus told Reuters that they have begun developing or are about to test new human shots to target the currently circulating version of the virus. Others, such as Sanofi, said they have vaccines for the H5N1 virus in stock and “stand ready” to produce up-to-date shots based on existing ones.

Notably, Moderna said its H5N1 vaccines will be made using the same mRNA technology used in its COVID-19 vaccines. The Massachusetts-based company plans to start testing the bird flu shots on humans in the first half of 2023 and could “very quickly” in an outbreak scenario, reported Reuters, citing Raffael Nachbagauer, Moderna’s executive director of infectious diseases.

Virus Spread

Scientists have been closely watching as the virus jumped from Europe to North and South America, leaving behind a devastating trail of nearly 200 million dead birds and other animals since the initial October 2022 outbreak in a mink farm in northwestern Spain.

In the United States, more than 52 million birds in 46 states have either died from H5N1 infection or have been put down due to exposure to infected birds since February, marking the worst disaster ever hit the American poultry industry.

A government worker examines chicks for signs of bird flu infection at a poultry farm in Darul Imarah in Indonesia's Aceh province on March 2, 2023. Chaideer Mahyuddin/AFP via Getty Images

H5N1 infections in humans are extremely rare, as the World Health Organization reported (pdf) just four cases last year, including two in Spain, a fatal one in China, and one in the United States.

In February, health authorities of Cambodia confirmed that an 11-year-old girl contracted and died from the disease. But Cambodian officials said there is no evidence of human-to-human transmission, further noting that the strain that caused the girl’s death isn’t the same one killing birds en masse in Europe and the Americas.

In the past 20 years, there have only been 868 people diagnosed with H5N1 infection, although 457 of them were killed by the virus, representing a 53 percent case fatality rate.

According to WHO Director-General Tedros Ghebreyesus, the phenomenon that mammals being infected by what primarily affects birds is rather new and deserves more attention.

“There have been several reports of mammals, including minks, otters, foxes, and sea lions having been infected with H5N1 avian influenza. H5N1 has spread widely in wild birds and poultry for 25 years, but the recent spillover to mammals needs to be monitored closely,” Ghebreyesus said at a Feb. 8 press conference.

“For the moment, WHO assesses the risk to humans as low,” he said, adding that since its first emergence in 1996, there have only been “rare and non-sustained transmission” of H5N1 to and between humans. “But we cannot assume that will remain the case, and we must prepare for any change in the status quo,” he said.

“As always, people are advised not to touch or collect dead or sick wild animals but to report them to the local authorities. WHO is working with national authorities and partners to monitor the situation closely and to study cases of H5N1 infection in humans when they occur.”