Vaccines aren’t just for kids. Thousands of adults go to the hospital each year for a serious (sometimes even deadly) disease they might have avoided if they had received the vaccination to prevent it. Universal immunization of infants and children, which began in the 1940s, has reduced the incidence of previously common and potentially fatal infectious diseases, including polio and smallpox.
But there are people who didn’t receive all the recommended vaccines—or they aren’t able to verify that they had them. As adults, they also may need special vaccinations if their job or lifestyle could expose them to particular diseases, or if they are traveling to a country that still has cases of a disease that is uncommon in the United States.
“Vaccines prevent you from getting sick, missing work, and spreading illness to family and friends, some of whom may be at risk of getting more severe disease,” says Marjorie Golden, MD, a Yale Medicine infectious diseases specialist. “Vaccines not only can prevent certain types of infection, like pneumonia or the flu, but also can prevent some kinds of cancer (like cervical cancer). Getting vaccinated has public health benefits as well—the more people in a community who are vaccinated, the harder it becomes for an infection to spread.”
How do vaccines work?
A vaccine triggers the immune system to help it build immunity to a disease. Our immune systems already have the capacity to react to diseases by producing substances called antibodies that remain in the body to combat their germs in the future. So, if someone had chicken pox, his or her body will remember those chicken pox germs and can fight them if they try to invade the body again.
With a vaccine, people don’t have to get the disease to develop immunity—the vaccine provides a tiny amount of a germ that has been weakened or killed; it triggers the same immune process but it's small enough that it won’t make them sick.
If a large enough portion of the population is immunized against the most threatening diseases, it is difficult for those diseases to spread, and people who are not immunized—because of a health condition or other reason—are protected from exposure. This is called herd immunity.
How are vaccines administered?
Most vaccines are administered by injection, although there are other delivery methods. Some vaccines may be given in capsule form, and some people ages 2 to 49 (not including pregnant women) may be able to take the flu vaccine by nasal spray.
What vaccines are available to adults?
Here is a list of vaccines for adults. Advice on which vaccines to get may vary depending on any chronic health conditions you may have, if you are pregnant, if you are an immigrant or refugee, or if if you are a healthcare worker or have another occupation that puts you at risk for exposure to serious diseases to which the general population is not exposed.
- Influenza vaccine. This is recommended for people 6 months or older (with rare exceptions), preferably early in the fall, before flu season begins. Flu shots are especially important for people who at high risk for flu-related complications. The latter includes pregnant women, people who are 65 or older, and people living with health conditions such as asthma or heart disease.
- HPV vaccine. This prevents human papilloma virus, which can spread through sexual contact, and is associated with genital warts and a variety of cancers. The vaccine is recommended between the ages of 11 and 12. In 2018, the Food and Drug Administration (FDA) approved the vaccine for adults up to age 45, so adults can talk to their doctors about whether they should consider it.
- Tetanus and diphtheria (Td). These are rare diseases that can have serious complications. Adolescents and adults should get the Td vaccine every 10 years as a booster (so-called because it boosts immunity when vaccines administered at an earlier age become less effective). An alternative that may be recommended is Tdap, which also protects against pertussis, or whooping cough.
- Mumps, measles, rubella (MMR) vaccine. This is given to children starting in infancy. But it should be discussed with your doctor if you were born after 1956 (most people alive at that time were exposed to a major measles outbreak and are therefore immune), or if you received the vaccine between 1963 and 1967—you may be part of a small population that had a formulation that is no longer in use.
- Shingles vaccine.This protects against shingles, a painful rash caused by the same virus that causes chicken pox. Shingrix, the vaccine that provides the greatest protection, is given to people ages 50 and older.
- Pneumococcal vaccines. These protect against a variety of infections, including pneumonia. They are recommended for adults who are 65 or older, and younger adults who smoke or have certain medical conditions.
Is there a vaccine for COVID-19?
Yes. Two vaccines, one developed by Pfizer-BioNTech and one by Moderna, were each found in clinical trials to be approximately 95% effective in protecting against COVID-19. They were given Early Use Authorization (EUA) by the Food and Drug Administration (FDA) in December 2020.
In February 2021, the FDA granted emergency use approval for a different type of vaccine, called a carrier, or virus vector, vaccine by Johnson & Johnson. It has 72% overall efficacy and 86% efficacy against severe disease in the U.S. It’s expected that several other vaccines will become available as well. Vaccine rollout depends on various factors, including age, occupation, and health status.
How do I know which vaccines I need?
The first step is to check your medical records to see which vaccines you received as a child. If you don’t have records, talk to your parents, or, if possible, ask the pediatrician you had as a child for records (although their records may be limited). Some state health departments also keep records of immunizations.
If you can’t get records of your vaccinations, you can talk to your doctor about getting what might be repeat vaccinations.
“If you’re not sure you’ve gotten the chickenpox vaccine, an antibody test can be done to see if you should get the vaccine,” Dr. Golden says.
Your doctor should let you know about booster shots or new vaccines that you might need as you age. Your doctor may also recommend particular vaccines based on your lifestyle (factors like smoking, particular occupations, and number of sexual partners may be considerations).
Many other factors may impact your eligibility or need for a vaccine. Talk to your doctor about any of the following situations:
- Pregnancy, possible pregnancy, or breastfeeding
- Any chronic diseases you may have
- If you aren’t feeling well on the day of the vaccine
- Allergies to the vaccine
- Weak immune system
- You’ve had your spleen removed
- Recent transfusions
- Guillain-Barre syndrome
- Plans to travel out of the country
Are vaccines safe?
Vaccines are the result of years of research and testing. Most health care professionals consider them to be very safe. The Centers for Disease Control and Prevention (CDC) and the FDA continue to monitor all vaccines licensed for use.
Severe side effects from vaccines are rare, and mild ones, such as soreness or redness at the site of a vaccination, go away in a few days.
Some people have expressed concern over the possibility of a relationship between vaccines and autism in children, and in the use of a preservative called thimerosal that was present in multiple vaccines in the 1990s.
“Thimerosal has never been shown to cause any harm other than local allergic reactions,” says Dr. Golden. However, due to public concerns, it was removed from childhood vaccines in 2001. Influenza vaccines are available with and without thimerosal, she says.
In fact, it may unsafe to avoid vaccines, since there are no cures for some of the diseases they prevent, and they can be deadly.
Is there anyone who should not be vaccinated?
If you are older or have a health condition, talk to your doctor about whether or not you should get a particular vaccine. In some cases, your doctor may advise against a vaccine or recommend waiting.
If you are not feeling well on the day of your flu vaccine, your provider might ask you to come back when you feel better.
How is Yale Medicine unique in the area of vaccines?
Yale Medicine infectious diseases doctors recommend all eligible patients get the appropriate vaccines.
“Other than access to clean water, vaccines are the single most important public health tool that we have to keep people healthy,” Dr. Golden says. “Vaccines not only save lives and health care costs, but they prevent unnecessary suffering. You should talk to your health care provider about which vaccines are right for you."
Some Yale researchers have focused their work on monitoring and evaluating the impact of vaccinations, and optimizing the effectiveness and cost-effectiveness of vaccination strategies, in addition to contributing to the development of new vaccines. Yale School of Medicine faculty also have worked closely with public health practitioners and policymakers at the CDC, the World Health Organization, and other organizations addressing issues surrounding vaccines.