Remember the last time smallpox, polio or diphtheria swept through the US? No? That’s because most of the once dangerous diseases we vaccinate against today are gone or well-controlled, popping up only in small clusters. Yet these success stories make it easy to forget the damage these illnesses can cause—and the importance of the vaccines that curb them. In fact, in recent years the Centers for Disease Control and Prevention (CDC) has estimated that only 21.8% of US adults have received all age-appropriate vaccines. The CDC has also noted that the national childhood vaccination rate is in decline, too.

Researchers are already spotting worrying clues that these trends may continue in the post-pandemic world. One study published in the New England Journal of Medicine found that a community’s low Covid-19 vaccination rate predicts a lower-than-normal rate of seasonal flu vaccination. Some infectious disease authorities are concerned this hesitancy will spill over into public beliefs about other vaccines, too.

Even before the Covid-19 pandemic, the World Health Organization (WHO) named vaccine hesitancy as one of the top ten threats to global health. But this intensified with the rollout of the Covid-19 vaccine, as we entered what the WHO called an “infodemic“: a flood of confusing, often conflicting information about the vaccine. A study published in the Journal of General Internal Medicine found that about 73% of Americans reported exposure to vaccine misinformation during the pandemic—and that this exposure is a direct predictor of vaccine hesitancy.

Because the reach of vaccine misinformation is so vast, experts want to set the record straight about infectious disease protection for all ages.

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Why are vaccines given at different ages?

The CDC’s standard vaccine schedule, outlined below, aims to protect individuals when they’re typically most vulnerable to a disease, explains William Schaffner, MD, the Medical Director of the National Foundation for Infectious Diseases and professor of infectious diseases at Vanderbilt University Medical Center. “It all has to do with how frequently the diseases you might encounter were historically associated with different age groups.”

Back in the day, he says, there were many infectious diseases that occurred primarily in infancy, childhood and adolescence. These rates of illness informed what we now consider “baby shots” and childhood vaccine schedules.

Childhood Vaccine Schedule

• At birth: Hepatitis B

• One to two months: Hepatitis B, DTaP (Diphtheria, tetanus, pertussis), Hib (Haemophilus influenzae type b), Polio, Pneumococcal, Rotavirus

• Four months: DTaP, Hib, Polio, Pneumococcal, Rotavirus, HepB

• Six months: DTaP, Hib, Polio, Pneumococcal, Rotavirus, Influenza

• One to two years: Chickenpox, DTaP, Hib, MMR (Measles, mumps, rubella), Polio (before 18 months), Pneumococcal, Hepatitis A, Hepatitis B

• Two to three years: annual flu vaccination

• Four to six years: DTaP, Polio, MMR, Chickenpox, flu

• Eleven to twelve years: Meningococcal conjugate vaccine, HPV, Tdap (DTaP booster), flu

If a child misses a shot, there’s no need to start over—a doctor can simply administer the right doses to get them back on schedule. There’s no upper limit to how many vaccines can be administered in one doctor’s visit, either (in most cases). “[Multiple vaccinations at once] is more a matter of individual tolerance than anything scientific,” Dr. Schaffner says.

In the United States, childhood vaccination rates are comparably high to the rest of the world, too. While vaccination coverage slipped (like, off a cliff) during the pandemic, it’s bouncing back today. Still, the CDC reports that for the 2020-21 school year, 94% of children had all required vaccines, which was one percentage point lower than the previous average. While this might not sound like a lot, that one point amounts to about 35,000 kids without vaccine protection—enough to jeopardize herd immunity against preventable diseases, like measles.

Check out 10 simple things all healthy kids have in common

Current rates for childhood vaccinations by age two:

• DTaP: 80.4%

• Polio: 92.5%

• Measles, mumps, rubella (MMR): 90.8%

• Haemophilus influenzae type b (Hib): 80.0%

• HepB: 91.4%

• Chickenpox: 90.3%

• Pneumococcal conjugate vaccine (PCV): 81.4%

Do childhood vaccines last for life?

Many of the vaccines you receive in childhood will protect you for life—but not all of them. “This has everything to do with the nature of a virus and how that particular virus interacts with the immune system,” Dr. Schaffner says. He points to measles as an example. “It’s a very stable virus, it doesn’t change—basically, the virus today is the same as it was in 1935.” So, once you get vaccinated against measles, your protection extends for life.

In contrast, illnesses like the flu and Covid-19 are not at all stable. Because these viruses mutate, infectious disease experts have to keep up with the changes and constantly rework vaccine compositions.

Still, the protection we get from certain longer-term vaccines simply declines over time. As examples: tetanus starts to wane after about 10 years, meningococcal nets you about eight years of protection, and the pertussis vaccine declines after four.

Plus, here’s what doctors want you to know about the Covid vaccine for kids

Do I need vaccines as an adult?

The CDC updates its adult immunization schedule on an annual basis—though, “compliance with the vaccination schedule really plummets when you get to adults.”

Sampling of Adult Vaccination Rates

• Pneumococcal vaccination ages 19-64: 23.9%

• Pneumococcal vaccination ages 65+: 67.5%

• Shingles vaccination ages 50+: 29.4%

• Shingles vaccination ages 60+: 39.1%

• Tdap vaccination ages 19+: 62.9%

• Annual flu ages 18+: 50.2%

• HPV ages 13+: 54.5%

• HepB ages 19+: 30.0%

He points to a few reasons for this trend. “First, people don’t recognize that vaccines are not just for kids,” explaining that these recommendations are rather recent to the last three decades or so. Additionally, “doctors who care for adults spend a relatively brief period of time with the patient at each visit—and they’re almost always preoccupied with diagnosis and treatment issues”—instead of preventive care, like vaccines.

And while almost all childhood vaccinations are covered by either insurance or governmental programs, there’s often a financial hurdle for adults. “In the United States—shame on us—we have not yet created a comprehensive adult vaccination program,” Dr. Schaffner says.

Learn more about why it’s critical that parents are up-to-date on their vaccines

What vaccines do I need as an adult?

Since not all vaccines offer life-long protection, adults need to top up their protection against illnesses like tetanus, Diptheria, and pertussis (whooping cough) with a Tdap booster. Some studies do suggest that the Tdap booster is unnecessary if you were fully vaccinated as a child, but the CDC still urges people to get it every ten years or with each pregnancy. The major reason for this is the risk these diseases pose to children. For example, whooping cough is no picnic for adults, but it can be fatal for kids…especially for infants too young to receive their first vaccine dose.

In 2022, the CDC also announced it recommends vaccination against hepatitis B for all adults under age 60. “We have been administering the hepatitis B vaccine universally to children,” Dr. Schaffner says. And the infection—which can lead to liver cancer down the road—has been largely eliminated among kids. “But it is continuing to occur substantially in adults.” He says that because the HepB vaccine is so effective, widespread adult vaccination could eliminate the hepatitis B virus from the population as soon as 2030.

Then there’s the HPV (human papillomavirus) vaccine. While commonly associated with preventing cervical cancer in women, it’s strongly recommended for all adolescents ages 11 and 12, says Dr. Ashley Lipps, an infectious diseases physician at Ohio State University’s Wexner Medical Center. As a sexually transmitted disease, unvaccinated men can spread the virus to women—but they’re at risk of other cancers HPV can cause, including head/neck, penile, and anal cancers. If the HPV vaccine was not available when you were an adolescent, the vaccine is strongly recommended for anyone under age 26, Dr. Schaffner says. That said, it’s approved in some cases up to age 45.

“I would also mention that everyone aged 65 and older is eligible for the pneumococcal vaccine,” he says. This vaccine protects against the most prominent bacterial cause of pneumonia (and it’s available to people under 65 with underlying health conditions).

All adults should also be vaccinated annually against influenza and up-to-date on the latest Covid booster, Dr. Schaffner adds. And the CDC updates its guidance on these shots—it’s totally safe to get them at the same time.

Recommendations for Adult Vaccinations (age 19+)

*note: some guidelines change for adults with additional risk factors or health conditions

• Flu vaccine: one dose annually

• Covid-19 booster: those eligible should receive as available

• Tdap: booster every 10 years, with each pregnancy, or for wound management

• MMR: one to two doses if born in 1957 or later and has not been fully immunized

• Varicella (chickenpox): two doses for those unvaccinated and have never had chickenpox

• Zoster (shingles): two doses for adults 50 years and older

• HPV: two to three doses before age 26 or before age 45 depending on your doctor’s recommendation

• Pneumococcal: for all adults over age 65, 1 dose PC15 followed by PPSV23 or 1 dose PCV20

• Hepatitis A: people with certain medical conditions or traveling overseas may require two to three doses depending on the vaccine

• Hepatitis B: two to four doses for all adults, depending on the vaccine

• Meningococcal: recommended for adults who haven’t been vaccinated and are a college student, in the military, or have a compromised immune system

Learn more about what vaccines you may need before traveling abroad

Can you get multiple vaccines at once?

In addition to a flu shot and Covid booster combo, most vaccines can be given at the same time. “There are a few exceptions to this,” Dr. Lipps says. The Prevnar-13 (PCV-13) should not be given with the meningitis vaccine or at the same time as the Pneumovax-21 (PPSV-23) shot. “This is because the immune response has been shown to be better when these vaccines are given at different times.”

Here are 40 more things your doctor wishes you knew about vaccines

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