The annual attempt to match the seasonal influenza vaccine with mutating flu viruses always is a bit of a gamble, and this year is no different.

In particular, the U.S. vaccine may not provide complete immunity to an H3N2 strain that has caused serious infections during the summer season in Australia. That’s all the more reason for healthcare workers to be vaccinated, as the protection it provides could be the difference between mild and severe illness.

Australian public health officials recently announced that “2017 has been characterized by high levels of influenza A (H3N2), which disproportionately affects the elderly. We have seen reports of high numbers of deaths in nursing homes this year and also amongst healthy adults. These are tragic events which underscore the message that influenza is a serious disease and that vaccination is absolutely critical for protecting individuals and the community. We do know that the 2017 vaccines have had a relatively good match with circulating strains, which provides the best opportunity for protection. There is, however, evidence that the effectiveness of the vaccines has been less than usual this year, particularly in terms of protecting the elderly against influenza A (H3N2).”1

It is unknown whether that H3N2 strain will circulate widely in the U.S., but the H3N2 strain in the current vaccine should provide some protection, clinical and public health officials said recently at a press conference at the National Foundation for Infectious Diseases (NFID) in Washington, DC.

“The proteins on the outside of that H3N2 virus are still quite similar to what’s in the current vaccine,” said William Schaffner, MD, medical director of the NFID and a professor of preventive medicine at Vanderbilt University School of Medicine in Nashville, TN. “We ought to be well prepared. This H3N2 strain is the one that usually causes more illness, more complications in older adults. So, if you needed another reason to be vaccinated, there it is. Best [to] get that protection.”

An H3N2 virus which eluded the vaccine strain caused a particularly bad flu season in the U.S. during the 2014-2015 season.

“Clearly, it was a severe season in Australia this summer,” said Daniel Jernigan, MD, MPH, director of the Influenza Division at the National Center for Immunization and Respiratory Diseases at the CDC. “Does that mean we’ll have a bad season this fall? We don’t know exactly, but we want to be prepared for that, and it’s one reason why it’s important to get your vaccine.”

The World Health Organization (WHO) has recommended that the next flu vaccine for the Southern Hemisphere include H3N2 A/Singapore/INFIMH-16-0019/2016-like virus. The vaccine that will be used in the U.S. and the other Northern Hemisphere countries will still have the H3N2 A/Hong Kong/4801/2014-like virus.

“There’s been a little bit of drift, some change, but there’s not been a significant mutation in the H3N2,” Jernigan said. “The [WHO] change was really made so that the vaccine that is made in eggs is a better vaccine. Right now, there are two vaccines. The [cell-based vaccine], which is made in cells [and] is made just with proteins — those aren’t affected by this change.”

According to the CDC, this new cell-based flu vaccine is made by growing viruses in animal cells rather than in the traditional chicken eggs.

With flu season comes the annual task of immunizing healthcare workers to protect themselves and their patients.

“And, just to make clear, it’s a patient safety issue,” Schaffner said. “We don’t want to give flu to the patients for whom we are providing care.”

Patsy Stinchfield, RN, senior director of infection prevention and control at Children’s Health Network in Minneapolis, said it is gearing up to get healthcare workers immunized.

“This is one of my tasks at Children’s: to get our 6,500 employees vaccinated,” she said. “I think it’s really about understanding the importance of it, making it easy and accessible [and] no charge. Making it such that we’ll come to you; where is your staff meeting? We do so many different interventions at Children’s. We don’t have a mandate as some hospitals do. But even in a unionized nursing environment, without a mandate, our staff are vaccinated at 94% year after year. It’s really emphasizing the importance and making it easy and accessible.”

Echoing those comments is Kathleen Neuzil, MD, MPH, FIDSA, director at the Center for Vaccine Development at University of Maryland School of Medicine.

“We do have a mandatory policy at the University of Maryland Medical Center, and we are also in the high 90 percentages,” she says. “It’s interesting. The nurses, the physicians, the people in the hospitals who have regular [patient] contact, we’re actually doing very well with those vaccination rates. It’s some of the other workers. We probably haven’t done as good a job at educating the support staff sometimes in hospitals.”

The seasonal flu vaccine never is 100% effective, but it is the best way to keep people out of the hospital and the morgue.

“And, as I like to say to some of my patients who say, ‘But Dr. Schaffner, you gave me the vaccine and I still got flu,’ I say, ‘I’m so pleased that you’re still here with us to complain, because you didn’t die of influenza,’” Schaffner says.


1. Australian Department of Health. Statement from the Chief Medical Officer on seasonal influenza vaccines. Sept. 27, 2017. Available at: Accessed Oct. 2, 2017.