The flu shot, which includes a killed version of the virus, cannot give anyone the flu. But since it is grown in eggs, it can cause an allergic reaction in people with egg allergies. The flu and the shot have also been linked to a rare nerve disorder called Guillain-Barre syndrome in a very small number of people, so anyone who has developed the disorder within six months of a previous flu vaccine should get professional advice before getting a flu shot, according to Dr. Shira Doron, an infectious disease physician and associate hospital epidemiologist at Tufts Medical Center in Boston.
People may also get a sore arm from a flu shot, which is delivered into the deltoid muscle of the shoulder, or a low-grade fever for a few days.
For those who don’t like needles, the second type of flu protection comes as a nasal spray called FluMist. This spray does contain live virus, so there is a small chance it could cause flu infection in someone with a compromised immune system. That’s why the spray form is not recommended for anyone with a weakened immune system, including pregnant women, children younger than 2, those undergoing cancer treatment or frail older people. Anyone who lives with an immunocompromised person could also theoretically pass on the virus and so would be advised to get the shot instead, Dr. Doron said.
Patients with asthma or recent wheezing should also avoid the nasal spray, which could worsen airway disease, she said. Children taking aspirin should probably avoid it as well, because aspirin use and flu has been linked to Reye’s syndrome, an extremely rare but dangerous swelling of the liver and brain.
Years of research have found no connection between thimerosal, a mercury-based preservative in vaccines, and autism. Multi-dose vials of the flu shot – but not other methods of delivery – do include a small amount of thimerosal, but at Tufts, they only purchase the single-dose vials, which don’t have the preservative, “just so that we never have to have that conversation,” Dr. Doron said.
Bottom line, Dr. Doron said, is that the risks of flu, which causes thousands of deaths each year, “are much higher than the risks of the flu vaccine.”
Vaccination helps people around you, too, including babies under six months, those whose bodies don’t mount a good response to the vaccine, and those who are too immunocompromised to get it.
“When you get the flu shot, it’s for yourself and it’s for everybody else,” she said.