Vaccination is perhaps the best way to protect yourself against many diseases including flu, but flu vaccine is no silver bullet. The vaccine’s effectiveness varies from year to year, depending on the closeness among that season’s viruses and the vaccine, which is usually reformulated each year. This winter in the United States, the vaccine’s performance has been very poor, leaving people more vulnerable to a virus that’s causing the flu.
The Centers for Disease Control and Prevention, which conducts studies annually to gauge the vaccine’s protective ability, has found that vaccination reduces the risk of getting flu by 40 percent to 60 percent during seasons when most circulating flu viruses are well-matched to the flu vaccine. Older people often have weak immune systems and a lower protective immune response after flu vaccination compared to younger, healthier people.
Some pharmaceutical companies are now producing flu vaccines and the virus in mammalian cells instead of chicken eggs to avoid the egg-adaption problem. It might work better than traditional, egg-based flu vaccines.