The 2018­-2019 flu season is here, and Kaiser Permanente is once again urging its employees and members to get vaccinated. While the effectiveness of the flu vaccine varies from year to year, the message from the Centers for Disease Control and Prevention has remained the same: to prevent flu, the best thing you can do is get a flu shot every year.

Flu vaccine is especially important for people at higher risk of developing severe flu, including pregnant women, young children, health care workers, the elderly, and people with chronic conditions such as diabetes, asthma and chronic obstructive pulmonary disease. A new CDC-led study, published on October 11 in Clinical Infectious Diseases, found that for pregnant women in particular, getting a flu shot reduced their risk of being hospitalized for flu-related reasons by an average of 40 percent.

Allison Naleway, PhD

The study was a partnership among CDC and other public health agencies and health care systems in Australia, Canada, Israel and the United States. Allison Naleway, PhD, an epidemiologist and vaccine researcher at the Kaiser Permanente Center for Health Research, is a study co-author.

“Expecting mothers face a number of risks to their health and the health of their baby during pregnancy, and getting the flu is one of them,” Naleway explained. “This study’s findings underscore the fact that there is a simple, yet impactful way to reduce the possibility of complications from flu during pregnancy: get a flu shot.”

Naleway is a site principal investigator for the Vaccine Safety Datalink, a national project funded by the CDC that links automated medical records data from several integrated health care delivery organizations to monitor vaccine safety. As a scientist on the front lines of vaccine research and surveillance, she often fields questions about the flu vaccine. Below, Naleway answers some of the most common questions she hears.

Why is the flu vaccine important?

Many people think of the flu as an inconvenience that causes a few days of misery at its worst, but the truth is that influenza can kill. Every year, hundreds of thousands of people end up in the hospital from the flu, and thousands of people die from flu-related causes. The flu vaccine isn’t perfect, but it’s our best defense. I encourage people to learn all they can about the flu vaccine, and the CDC’s “Key Facts About Season Flu Vaccine” is a great place to start.

Are there people who shouldn’t get the vaccine?

Many formulations of the flu vaccine are grown in chicken eggs, so people with egg allergies should talk to their health care provider before deciding whether to be vaccinated. Also, people who have had severe reactions to the flu vaccine in the past should talk to their health care provider before they decide whether to be vaccinated again. That said, severe reactions to the vaccine are very rare. Perhaps one in a million people vaccinated might have an allergic reaction or develop a rare paralytic illness. More common reactions include redness at the injection site, soreness, or a slight fever — mild symptoms that are outweighed by the vaccine’s benefits.

Is there a chance that I will still get the flu even if I do get the vaccine?

The flu vaccine is reformulated every year, so its effectiveness varies from year to year. It depends on how well the vaccine is matched to the particular viruses that are causing the flu. Scientists usually do a pretty good job of predicting which flu viruses are going to move from the Southern hemisphere into the Northern hemisphere, but sometimes they miss the mark. That’s what happened in the spring of 2009, when H1N1 spread up through Mexico into the United States. Experts didn’t see that coming, so we already had a large wave of illness before we had a vaccine to prevent it.

If the vaccine isn’t always effective, why should I get it?

The vaccine has been studied extensively and it’s very safe, so there’s very little downside to getting it. The flu can be quite serious and can cause severe symptoms including cough, sore throat, high fever, body aches, chills, fatigue and headaches. Again, while most people recover after a few days, many people end up in the hospital, and there are still thousands of people who die each year from complications of the flu.

Can the flu vaccine cause the flu?

Let me say emphatically that the flu vaccine does not cause the flu. The injectable vaccine contains a killed virus, so there’s no chance that it can give you the flu. We usually give the flu shot in September or October when a lot of other viruses are circulating, so when someone gets sick after getting the flu vaccine, it’s just a coincidence that they caught some other bug about the same time they were vaccinated.

Do you get the flu vaccine?

Yes! I get the vaccine every year — and so does my family.