Doctor: Obesity worsens influenza
Bad cases more likely in overweight people, flu researcher says
The flu vaccine is less effective for obese people, who are also likely to experience more severe flu symptoms, Dr. Stacey Schultz-Cherry said Saturday, speaking at the annual Vaccine Development Center of San Antonio Conference.
Schultz-Cherry, a faculty member at St. Jude’s Children’s Research Hospital in Memphis, Tenn., and deputy director of the World Health Organization Collaborating Centre for Studies on the Ecology of Influenza in Animals and Birds, was one of several keynote speakers at the conference this weekend, discussing research into how obesity affects the spread of and vaccination against the flu.
Developments to improve the efficacy of the flu vaccine are underway, with a goal of increasing how many strains of the flu virus against which the vaccine can provide immunity.
“One thing we need to consider is the population we’re trying to vaccinate,” Schultz-Cherry said. Pregnant women, young children, the elderly and people whose immune systems are compromised are already considered high-risk groups, and obese people could be another, she said.
During the 2009 “swine flu” pandemic, studies suggested for the first time that overweight and obese people were more likely to develop severe illnesses, she said.
In comparing maps showing flu activity last year and obesity rates by state, “the higher the obese population, the more likely you are to have hospitalizations and ICU stays and even mortality,” she said.
Obesity is a growing concern and has nearly tripled since 1975, according to WHO, meaning there’s a growing population of people who may be more susceptible to the flu, less able to fight the virus and more likely to spread it to others for longer.
That’s in part because obesity causes chronic low-level inflammation, “so they’re basically immuno-compromised in many ways,” Schultz-Cherry said.
In research looking at mice, the obese animals’ bodies were not able to control the virus’s spread the way the bodies of lean mice could.
“Obese animals mount a much lower response” than leaner mice, she said. The chronic inflammation makes it harder for the body to respond, she said, “allowing the virus to take off.”
The microbiome, or the microorganisms inside the body, also play a role, she said, which is a subject for further study.
Obesity also makes it harder for the body to clear the virus or the bacterial infections that can follow, Schultz-Cherry said.
Research on ferrets and studies of humans have also showed similar results related to flu susceptibility and transmission.
The flu vaccine causes the body to develop antibodies, which pro---
tect against strains of the flu virus. But when vaccinated, the obese mice have been less responsive and less likely to produce those antibodies, she said.
In studying humans, overweight and obese people were more likely to lose their antibodies faster after receiving the vaccine, making them again more susceptible to the virus.
That creates “the perfect storm,” she said. “We have, potentially, a more susceptible population, higher viral load, more se- vere disease, longer shed and a changing virus. What are we going to do?”
The first answer to solving that, she said, is to keep vaccinating.
The risk of having a heart attack or stroke when you get the flu is significant for overweight and obese people, and the vaccine reduces that likelihood, even if it’s less effective, she said. “So if for no other reason, get your flu vaccine.”
Further research is ongoing, Schultz-Cherry said, and could include looking into how age and gender factor into susceptibility and transmission. “There’s so much we still don’t know,” she said.
The seventh annual conference, which started Friday at the Eilan Hotel, featured keynote speakers from across the U.S., as well as student research presentations.
The Vaccine Development Center of San Antonio opened in 2012, with three goals, Bernard Arulanandam said. It was created to increase awareness of the importance of vaccines, foster research into vaccines across scientific disciplines and provide opportunities for trainees.
Arulanandam, a professor and vice president for research at University of Texas at San Antonio, is a member of the conference committee and a co-director of the cen- ter.
He said sharing factual information about vaccines is key to fighting preventable diseases, such as whooping cough, as well as slowing the spread of viruses such as influenza.
“The issue of misinformation about vaccination has led to outbreaks of childhood infections that can be prevented,” Arulanandam said. Understanding how to make vaccines more effective and more universal, to immunize against more strands of viruses, should be a national priority, he said.