Even though the Centers for Disease Control and Prevention does not include a booster in its definition of “fully vaccinated,” research shows that an additional dose of an mRNA vaccine, either Pfizer-BioNTech or Moderna, is required for protection against all COVID-19 variants. But only 50 percent of Connecticut residents, and slightly more than 44 percent of all Americans, have received a booster.

If you’re boosted and get infected, it’s likely you’ll experience milder symptoms than if you were merely fully vaccinated.

“Our biggest worry is that when it’s out of sight, out of mind, we tend to be binary: ‘COVID is gone,'” says Dr. Ulysses Wu, Hartford HealthCare’s System Director of Infection Disease and Chief Epidemiologist. “We forget about boosters, we forget about vaccinations. We certainly don’t want a huge swarm in October of unvaccinated and unboosted individuals. So make sure you stay up to date not just on COVID vaccinations but all other vaccinations as well.”

In Connecticut, the younger you are the less likely you’re boosted. (In the graphic below, select the “Additional dose” categories from the dropdown menu.)

Feeling intimidated by side effects from the first two mRNA doses? New data from Spain, where 91 percent of the population has been vaccinated, suggests milder symptoms after the booster dose whether because of an immune response from the initial vaccination or through a previous infection.

Most side effects from close to 300 million mRNA doses administered in the first six months of their availability in the United States were mild and lasted no more than a few days, according to research published this month in The Lancet. The second dose, the researchers found, produced the most significant side effects. These included body aches, fever and other flu-like symptoms.

The booster dose, if you haven't already received it, should produce milder side effects.

"Remember, says Dr. Wu, "that the definition of being fully vaccinated still remains just your primary series. But we know clinically that is not true. You do need to be boosted to really be considered from a clinical standpoint to be fully vaccinated."