Can Vaccines Make Me Sick?

Experts say it is extremely unlikely that you would get sick from a vaccine.

Why? When a virus makes you ill, the immune system works to identify, attack, and remember it for the future. Most vaccines are made with dead ("inactivated") or weakened ("live attenuated") virus. The immune response is similar, but the virus can't reproduce and cause illness.

Then how come my friend got sick after a shot? He or she might have been exposed to a virus just before or just after vaccination, so the illness was a coincidence.

Well, I felt lousy after a shot. Vaccines can have minor side effects. Live attenuated vaccines like the nasal spray for flu may be more effective in some people than the dead viral particles used in the flu shot, but they can cause symptoms such as congestion, runny nose, sore throat, or cough. (They also are not recommended for children under 2, adults 50 and older, and people with asthma or compromised immune systems.)

Why do you say sickness is extremely unlikely? In live-virus vaccines, "attenuated pathogens have the very rare potential" - 0.0002 percent to 0.0004 percent for the oral polio vaccine - "to revert to a pathogenic form and cause disease in vaccinees or their contacts," according to the World Health Organization.

Many things we do every day - crossing the street, driving a car, eating fresh produce or a rare burger - are far riskier.

- Don SapatkinEndText