Fall shots: Who’s most vulnerable to RSV, COVID, and the flu?

Yellow, red, and greenish autumn leaves with a vaccine syringe and vial posed against a white background; concept is fall vaccines

The fall calendar doesn’t just warn us of impending cold temperatures: It also points toward seasonal upticks in cases of RSV (respiratory syncytial virus), COVID, and influenza. These respiratory viruses were dubbed a “tripledemic” last year. After they collided to overload health care systems across the country, hospitalizations rose in tandem for all three illnesses over the fall and winter months.

Warding off severe cases — which may lead to hospitalization or death — should be top of mind, especially for those who are most vulnerable, a Harvard expert says. And updated versions of all three vaccines are now available to help protect us.

Why do cases of flu, RSV, and COVID typically rise in fall?

“This is typically the time of year we start to see viral infections increase, which has a lot to do with kids going back to school,” says Dr. John Ross, an assistant professor of medicine at Harvard Medical School who is board-certified in infectious diseases.

“Also, we’re starting now to have weather that’s more favorable for viral transmission, particularly lower humidity. Viruses survive better in dry air. And drier air also affects our airways and makes them more vulnerable to being infected.”

Who is eligible for each shot?

Eligibility recommendations vary by age and vulnerability to serious illnesses. Additionally, some shots are designed to help protect specific groups against serious illness.

The CDC recommends these shots for the following groups.


  • Babies under 8 months and older infants at risk of severe RSV: A new shot, nirsevimab (Beyfortus), provides antibodies that protect against RSV for about five months.
  • If you’re pregnant: One vaccine (Abrysvo) is approved at 32 weeks to 36 weeks of pregnancy. Having this shot during pregnancy protects infants during the first six months of life.
  • If you’re over 60: Two vaccines (Arexvy and Abrysvo) are approved. Ask your health provider if you should consider getting one.


  • Everyone 6 months and older should consider getting one of the updated COVID boosters, which were approved and authorized for emergency use by the FDA in early September. 
  • Age 5 and older: Regardless of prior vaccination, children and adults are eligible for one dose of an updated mRNA vaccine if it’s been at least two months since their last COVID vaccine, the FDA says.


  • Everyone 6 months and older should receive a flu vaccine.
  • Different vaccines are approved for different age groups and for people with certain health issues or allergies. Most protect against four strains of flu virus (quadrivalent vaccines) expected to circulate this season.
  • Three vaccines could potentially be more effective for people over 65: Fluzone High-Dose Quadrivalent vaccine; Flublok Quadrivalent Recombinant vaccine; and Fluad Quadrivalent adjuvanted flu vaccine. If these are not available, it’s fine to get any other flu shot approved for your age and health issues or allergies.

Who is likely to benefit most?

Getting the right vaccines can help people avoid missed work or school days and running the risk of making others sick. And the protection offered by these shots is especially important for certain groups.

For all three viruses, the people most vulnerable to severe illness are similar, Dr. Ross says, including

  • adults 65 and older
  • those with compromised immune systems or underlying lung conditions such as COPD and asthma
  • those who are pregnant.

“Certainly with COVID and flu, pregnancy outcomes are worse with those infections,” Dr. Ross says. “I’m not saying that RSV isn’t a risk for pregnant mothers, but there’s not much data. The reason pregnant women are offered RSV vaccination is so the maternal antibodies they produce protect the newborns, because they’re at very high risk for RSV with very bad outcomes.”

Additionally, an even wider range of people are more prone to complications from the flu, according to the CDC. This includes

  • infants under 2
  • people with heart disease, neurologic conditions, blood disorders, endocrine disorders such as diabetes, obesity, kidney disease, liver or metabolic disorders
  • people who have had a stroke.

What else should you know about flu, COVID, and RSV shots?

Beyond broad guidance determining who’s eligible for each type of vaccine, Dr. Ross offers other useful insight that may guide your choices.

When is the best time to get a flu shot?

The CDC recommends getting a flu shot in September or October, and Dr. Ross agrees. “These are usually the months the flu vaccine becomes available and vaccine clinics are easiest to find,” he says. “My personal approach is just to get the vaccine when it’s available, so you don’t forget.”

Will the updated COVID vaccines protect against newer strains of the virus?

The latest mRNA shots by drugmakers Pfizer and Moderna are monovalent, meaning they protect against one variant — XBB.1.5, the most recent to descend from Omicron earlier in 2023. Though that strain is no longer dominant, the boosters should still guard against closely related subvariants that are now circulating, Dr. Ross says. “People can feel comfortable about their protection regardless,” he says.

What else should I know about RSV shots?

The version meant for infants, Beyfortus, isn’t a vaccine at all. It’s a monoclonal antibody product that directly delivers antibodies that protect babies for the duration of a single fall-winter RSV season. These antibodies can prevent RSV or lessen its severity.

Dr. Ross says adults over 60 considering RSV vaccination should be aware of the potential for two rare but potentially serious side effects of the nervous system: the autoimmune conditions Guillain-Barre syndrome and acute disseminated encephalomyelitis, or ADEM. Guillain-Barre can lead to bodywide paralysis, while ADEM can cause weakness and seizures. The risk of these side effects after RSV vaccination in adults is about one in 7,000 — far higher than occurs after flu vaccination, Dr. Ross notes.

“If you’re a totally healthy 60-year-old, I’m not sure it makes sense to get the RSV vaccine,” he says. “It’s a conversation you should have with your doctor.”

How should I schedule shots if I’m getting several vaccines?

Research suggests that it’s safe to get both flu and COVID vaccines at the same time. Reactions (such as muscle aches, fatigue, and headache) are slightly higher when flu vaccine and an mRNA COVID vaccine are combined, according to one study, though these reactions usually are mild and disappear quickly.

“Because RSV vaccines are newer, I don’t think we know much about combining these shots with other vaccines,” says Dr. Ross. Scheduling this vaccine separately is a good idea, although you should talk to your doctor about potential risks and benefits for your situation.

About the Author

photo of Maureen Salamon

Maureen Salamon, Executive Editor, Harvard Women's Health Watch

Maureen Salamon is executive editor of Harvard Women’s Health Watch. She began her career as a newspaper reporter and later covered health and medicine for a wide variety of websites, magazines, and hospitals. Her work has … See Full Bio View all posts by Maureen Salamon

About the Reviewer

photo of Howard E. LeWine, MD

Howard E. LeWine, MD, Chief Medical Editor, Harvard Health Publishing

Dr. Howard LeWine is a practicing internist at Brigham and Women’s Hospital in Boston, Chief Medical Editor at Harvard Health Publishing, and editor in chief of Harvard Men’s Health Watch. See Full Bio View all posts by Howard E. LeWine, MD


7 organs or glands you may do just fine without

Colorful discs with illustrations of different body parts and organs (appendix, kidneys, eye and more)


There was a time when pediatricians routinely recommended tonsil removal, even for healthy children — including me. As far as I can tell, I suffered no ill effects — plus, I got extra ice cream!

That practice is no longer routine. But it does raise an interesting question: Why do we have body parts that can be safely removed? If they’re not needed, why do humans have them in the first place?

One theory is that these nonessential organs and glands once served important roles in the lives of our evolutionary ancestors but now represent anatomic remnants. For example, it was long thought that the appendix helped our predecessors digest food, but over thousands of years became obsolete. And some organs are supremely useful during certain stages of life, but then become expendable.

Seven (mostly) unnecessary body parts

Here are seven removable parts of the body:


This organ is about the size of your little finger and hangs from the lower right side of your colon. For reasons that aren’t clear, this part of the intestinal tract sometimes becomes blocked, infected, or inflamed. Aptly enough, the word appendicitis means inflammation of the appendix. While it may settle down with antibiotic treatment, emergency surgical removal (an appendectomy) is often necessary.


A network of lymph nodes throughout the body is part of the immune surveillance system that helps trap dangerous invaders such as bacteria and viruses. Consider your two tonsils as larger, specialized lymph nodes watching out for these intruders. They are located at the back of the throat just to the sides of and behind the uvula, the dangling piece of tissue above them.

Now, removing the tonsils (a tonsillectomy) is only recommended for people with repeated bouts of bacterial throat infections such as strep throat, a condition common in children. Once removed, other lymphoid tissue, including the actual lymph nodes, can take over the job of the tonsils.


Situated in the back of the nose where the nasal passages meet the mouth and throat, adenoids are similar to tonsils. They can also become inflamed, infected, and swollen. So when the tonsils are removed, the adenoids are generally removed at the same time. The combined procedure is called tonsillectomy and adenoidectomy. As is true for the tonsils, other lymphoid tissue takes over when the adenoids are gone.


The gallbladder sits just under the liver in the upper right part of the abdomen. It stores bile made in the liver and releases it into the digestive tract when needed to help digest fatty foods. The gallbladder may need to be removed (a cholecystectomy) if it becomes inflamed, a condition called cholecystitis. Most often this occurs due to infection or gallstones, which are a hardened collection of bile. In some cases, rest and antibiotics can control gallbladder inflammation so removal can be delayed or even avoided.


This remarkable reproductive organ has a single purpose: to support fetal growth until birth. When necessary, the uterus can generally be removed (hysterectomy) without impairing health. Common reasons for removal include painful or excessive menstruation, benign growths called fibroids that cause pain or bleeding, or cancer.

Thymus gland

This small gland sits high in the upper chest behind the breastbone. In a fetus or newborn, it’s quite important in the development and maturation of the immune system. But adults can live well without it. Surgery to remove the thymus (a thymectomy) may be recommended if the thymus becomes cancerous, or if a person develops the autoimmune condition myasthenia gravis.


Like adenoids and tonsils, the spleen is made up of lymphoid tissue. It filters the blood, removing infectious organisms, aging blood cells, and other abnormal cells traveling through the bloodstream. But sometimes the spleen becomes overactive and begins removing healthy cells.

For example, idiopathic thrombocytopenic purpura (ITP) may develop when platelets (clotting blood cells that prevent excessive bleeding) are removed from circulation. With few platelets left in the bloodstream, bruising and bleeding may be life-threatening. Although medications can help, removal of the spleen (a splenectomy) may be necessary. Or sometimes trauma to the spleen, especially after sports injuries and car accidents, causes internal bleeding, which may lead to splenectomy.

People who lack a spleen are more prone to certain infections, so if removal isn’t urgent, a number of vaccinations are recommended before splenectomy.

The bottom line

I’ve heard it said that at least half of all body parts are unnecessary. That’s a myth. But as with most myths, there is some truth to it: there are indeed many body parts that can be safely removed. That said, it’s generally best to avoid unnecessary surgery and keep the parts you were born with if you can.

Sure, you can survive and thrive despite having your appendix removed. But it’s worth keeping in mind that our understanding about so-called spare parts may change over time. The appendix is a good example: researchers have discovered that the appendix may play a role in immune development and stores “good bacteria” to repopulate the gut in case of future illness. And there is evidence that removing the thymus may slightly increase the risk of cancer, autoimmune disorders, and death.

Someday we may discover important functions for other body parts we now consider expendable. And maybe then I’ll wish I had my tonsils back.

About the Author

photo of Robert H. Shmerling, MD

Robert H. Shmerling, MD, Senior Faculty Editor, Harvard Health Publishing; Editorial Advisory Board Member, Harvard Health Publishing

Dr. Robert H. Shmerling is the former clinical chief of the division of rheumatology at Beth Israel Deaconess Medical Center (BIDMC), and is a current member of the corresponding faculty in medicine at Harvard Medical School. … See Full Bio View all posts by Robert H. Shmerling, MD