With flu season swiftly approaching in a country already battling a resurgence of the coronavirus, experts are urging Americans to avail themselves of any and all vaccines they are eligible for — whether it’s their first coronavirus vaccination, a booster vaccine dose to combat waning immunity or a flu shot.

“It’s terribly important” to get both the flu and coronavirus vaccines, said William Schaffner, medical director of the National Foundation for Infectious Diseases. “They are both very nasty respiratory viruses that can make many people very, very sick.”

And because the coronavirus and flu vaccines “train your immune system to protect you against completely different viruses,” getting a shot that protects you against one virus will not offer any protection against the other, said Kelly Moore, president and CEO of the Immunization Action Coalition.

“It’s like protecting yourself against a bee and a wasp, both of which can sting you,” Schaffner said. “You’ve got to protect yourself against each one separately.”

The Centers for Disease Control and Prevention recommends that everyone be vaccinated against the flu by the end of October. This year, that time frame could overlap with the period when many Americans may become eligible for a booster dose of the coronavirus vaccine.

Extra doses of coronavirus vaccine are already being administered to immunocompromised people. Despite some disagreement among experts about the need for additional shots at this time, the Food and Drug Administration and the CDC have now green-lit boosters for eligible Americans who received any of the three available coronavirus vaccines. Both agencies have signed off on mixing and matching the shots.

With many more Americans eligible for coronavirus boosters during flu season, here’s what experts say you need to know.