By Dr. Max Gomez

NEW YORK (CBSNewYork) — First, it was the two-shot COVID vaccines, then came a third booster shot, and now, a certain group of people may get a fourth mRNA COVID-19 vaccine.

As CBS2’s Dr. Max Gomez reports, vaccines are said to be the greatest advances in public health history, but they depend on the recipient’s own immune system to respond to the shot by making antibodies and killer cells to fight off an invading germ.

READ MORE: First U.S. Case Of Omicron Variant Detected In California

But not everyone can do that.

COVID VACCINE

“That minority of our population who is moderately or severely immunosuppressed and not capable of responding well, immunologically, to the vaccine in general,” said Dr. Bruce Farber, chief of epidemiology at Northwell Health.

That includes people with certain cancers, those taking immuno-suppressing drugs for transplants or some other diseases. A recent study found that this group was 485 times more likely to end up in the hospital or die from COVID-19.

READ MORE: New York Opening 18 New COVID Vaccine Pop-Up Sites For Children Statewide

For them, the Food and Drug Administration and Centers for Disease Control and Prevention approved a third full dose in an attempt to enhance their immune response, and now the FDA has authorized a fourth shot of half-dose Moderna or full dose Pfizer for immunocompromised people.

There is no additional shot for Johnson & Johnson.

CORONAVIRUS PANDEMIC

“This is a very vulnerable group of people, and I think we need to bend over backwards to do whatever we can to prevent them from getting sick,” Farber said.

MORE NEWS: CDC Steps Up Screening For Omicron Variant At Area Airports

But this group of people still needs to be very careful about their possible exposure to COVID. That means mask wearing and social distancing, even with three or even four doses.

Dr. Max Gomez