Written by By  Sarah Weisel, CNN
Pharmaceutical company Pfizer announced in a recent press release that new evidence suggests it may only partially prevent infections with a new, strain-specific strain of influenza A(H3N2) virus.
The Zika virus has recently been associated with a new strain of H3N2 virus that is associated with subclinical disease and a need for antiviral treatment, according to a study published in the New England Journal of Medicine.
The new strain of virus “is associated with more severe disease and widespread transmission than with other influenzas of the same family,” the study said. “Further investigation is needed to understand the subclinical and epidemiologic association with this new virus strain and associated subtype.”
If all people should carry an antigen-specific vaccine, the vaccine could last for months or even years, creating a large and lasting pool of vaccinated people from which to collect and adapt vaccine strains. Unfortunately, if more people are under the protective umbrella of the vaccine, their protection may be compromised.
Pfizer’s Flucelvax-19 vaccine is specific to this new strain of H3N2 influenza A, but at this time, the company has not decided whether to develop another “carrier” vaccine that can protect against the new strain, according to an announcement by Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases, who did not take part in the study.
Pfizer “reviews safety data in experimental vaccines closely and may slow down development of a carrier vaccine if additional safety data are not satisfactory,” he said.
The new strain was identified through blood samples from patients who became ill and reported containing the mutated virus, Fauci said. “Based on the emergence of this novel H3N2 virus in the Americas, the World Health Organization (WHO) responded by initiating routine surveillance of patient laboratory samples from affected areas to identify potential circulating strains.”
The new strain is generally expected to spread around the world in the current severe flu season, according to the WHO.
The agency issued a global alert and strain request as well as guidance for national health departments to conduct rapid assessment of surveillance networks for circulating viruses, it said.
While flu has begun spreading among people who had not previously been infected with the virus, the best protection against severe illness comes from the vaccine, which is typically developed in advance of the flu season. Vaccines work by introducing a live but weakened form of the flu virus into the body’s immune system, allowing it to learn how to protect itself against the real thing.
According to a study published in the Journal of Applied Microbiology, the new strain of flu causes more severe illness — as many as four times that of a normal strain of H3N2 virus — and is more easily passed between people in contact with a partner. If a partner is infected, the virus could pass on to children and other vulnerable people, potentially exposing them to a more serious illness.
“There’s a possibility that the virus has mutations that let it evade vaccine protection,” said Dr. Benjamin Moskowitz, associate professor of medicine and pathology at Beth Israel Deaconess Medical Center and Harvard Medical School. “The objective for a flu vaccine is to put it in people and it’s somewhat magical that if it can’t do that, it cannot make the antibody response that the body normally makes. …There’s a change in the virus sequence, so vaccine effectiveness really depends on having the right number of parts.”
It was hoped that three injections would provide sufficient protection against the new strain, but none of the patients who participated in the study received all three. The results showed that 45% of people who received two vaccinations were protected against the new strain compared with 35% of those who received one vaccination.
“This is not the last word on how effective the vaccine is. Clearly, there’s still a way to go for a few more years of development,” Moskowitz said. “One thing is for sure: this is not a new strain that happened to appear. This was a new strain identified.”
This article originally appeared on CNN.com