As COVID-19 continues to evolve, so does the knowledge concerning how to protect ourselves and others.

Amid projections of a cold-weather surge in cases and concerns about new variants, experts continue to urge all who are eligible be vaccinated. Yet fewer than 30 million Americans have received the newest booster, which was released in early September.

The Cigna Newsroom asked Dr. Nalini Raju, a senior medical director who leads Cigna's Emerging Virus and Infectious Disease (EVID) Workgroup and supports Cigna’s COVID response, to share the best ways to stay healthy this fall and winter. Read on for her responses.

How does the newest booster differ from what was available earlier?

This new version is a bivalent vaccine, which means it contains two different messenger RNA components of the virus that causes COVID-19. One targets the original coronavirus strain, and the other targets the omicron subvariants, BA.4 and BA.5. Currently, BA.5 accounts for approximately 40 percent of cases in the United States. However, we believe the current vaccines will also provide some protection from the newer variants that have begun circulating.

Who is eligible for the omicron booster? How do I know if I should get it?

The Centers for Disease Control (CDC) recommends that adults and children 5 years of age and older receive one updated (bivalent) booster if it has been at least 2 months since their last dose of the COVID-19 vaccine, whether that was the second and final dose in the primary series or one of the original (monovalent) booster shots.

The CDC has not yet expanded the updated booster to children younger than 5.

The CDC offers a personalized interactive eligibility tool to guide people who are unsure if they or their children should or can get the booster. Two versions are online, one for adults and one for children through age 18.

I’ve had COVID and recovered. Do I need a booster shot?

Yes. Recent data suggests the effectiveness of the vaccine at preventing infection or severe illness decreases over time. This is especially true for certain groups of people, such as those 65 and older and those who have a compromised immune system. Data shows that receiving an mRNA booster such as Pfizer or Moderna increases the immune response. This improves protection against getting a serious COVID-19 infection.

The continuing emergence of variants further emphasizes the importance of vaccination, boosters, and prevention efforts needed to protect against COVID-19.

Are there any reasons to wait to get the new COVID booster?

If you have recently recovered from COVID-19, you may consider delaying your next vaccine dose (primary dose or booster) until 3 months after your symptoms started or – if you had no symptoms – when you first received a positive test result. That’s because reinfection is less likely in the weeks to months following infection because of the antibodies created by your body’s immune response.

However, certain factors could be reasons to get a vaccine sooner rather than later. Those factors include personal risk of severe disease, risk of disease in a loved one or a close contact, a high level of COVID-19 in your community, and the most common COVID-19 variant that is currently causing illness. To help you weigh all these factors, you should discuss optimal timing with your doctor.

Who shouldn’t get the booster?

If you had a severe or immediate allergic reaction to a previous dose of this vaccine or any of its components, you should not receive another dose. If this is the case, please talk it over with your physician.

I haven’t been vaccinated yet. If I get the first two shots, will I be protected from omicron? Would I also need a booster?

You are considered fully vaccinated after receiving two doses of the vaccine. The definition of fully vaccinated does not include a COVID-19 booster. Fully vaccinated, however, is not the same as having the best protection. People are best protected when they stay up to date with COVID-19 vaccinations, which includes getting a booster when eligible.

I’ve never had COVID. Do I really need the shot? Maybe I’m immune to the virus.

Yes, because COVID-19 vaccination significantly lowers your risk of severe illness, hospitalization, and death if you get infected. Compared to people who are up to date with their COVID-19 vaccinations, unvaccinated people are more likely to get COVID-19, much more likely to be hospitalized with COVID-19, and much more likely to die from COVID-19.

Like all vaccines, COVID-19 vaccines are not 100% effective at preventing infection. Some people who are up to date with their COVID-19 vaccinations will get a COVID-19 breakthrough infection. However, staying up to date with your COVID-19 vaccinations means that you are less likely to have a breakthrough infection and, if you do get sick, you are less likely to get severely ill or die. Staying up to date with COVID-19 vaccination also means you are less likely to spread the disease to others and increases your protection against new variants of the virus that causes COVID-19.

How long will this shot protect me?

Scientists are researching how long COVID-19 vaccine protection lasts. COVID-19 vaccines are effective for preventing severe illness, hospitalization, and death. However, this protection decreases over time, especially for certain groups of people. The CDC continues to review evidence and updates the guidance on its website as new information becomes available. Resources include updated COVID-19 booster recommendations and recommendations for people who are moderately or severely immunocompromised.

I heard this version wasn’t tested on humans before being rolled out. Why should I trust that it’s safe?

The updated vaccines were authorized by the U.S. Food and Drug Administration (FDA) based on the demonstrated safety and effectiveness data from the original COVID-19 vaccines as well as trials of the bivalent vaccine in mice. The FDA also considered data from human trials by Pfizer and Moderna of a similar updated vaccine that targeted Omicron BA.1. Human trials of this updated booster are underway. Given the rate at which the virus is changing, however, effectiveness results are likely to be less relevant.

Although COVID-19 vaccines were developed in a shortened time frame, research and development on similar vaccines been underway for many years. All vaccine development steps were taken to ensure safety and effectiveness of the COVID-19 vaccine, including three phases of clinical trials and full data review.

Like every vaccine approved for use in the United States, COVID-19 vaccines continue to be monitored for safety and effectiveness. Hundreds of millions of people in the United States have safely received COVID-19 vaccines.

I’ve been hearing about a “tridemic.” What is it, and how can I protect myself?

Experts are concerned that high levels of the flu, respiratory syncytial virus (RSV), and COVID will converge over the next months, overwhelming our health care system. To protect yourself and to do your part to safeguard others, stay up-to-date with your COVID vaccines and talk to your doctors about getting flu shots and the best ways to protect your children from RSV.