When a critical portion of the community is vaccinated against a contagious disease, most of the population is protected since there is little opportunity for an outbreak. This is known as “community immunity.” Even those not eligible for certain vaccines — infants, pregnant women and immune-compromised individuals — get some protection because the spread of the disease is contained.

In the United States, vaccines are held to the highest safety standards; we have the safest, most effective vaccine supply in history. The FDA requires years of testing before a vaccine is approved and licensed. Through the Vaccine Adverse Event Reporting System, the CDC and the FDA continue to monitor vaccines for adverse effects and, if necessary, initiate appropriate action. This may include changing vaccine labels or packaging, distributing safety alerts, inspecting manufacturers’ facilities and records, withdrawing recommendations for use or revoking the vaccine license.

Immunizations are not just for children. Adults continue to need protection against a variety of infectious diseases. The immunizations you need are determined by age, lifestyle, high-risk conditions, type and location of travel and previous vaccinations.

The influenza virus is easily spread and can be very serious, especially for people over 50. Get a flu shot at a doctor’s office, health clinic, pharmacy, senior center or workplace each fall before flu season starts. Each year, medical experts and the CDC predict which three strains of flu are most likely to strike and then produce vaccine from these strains. A flu shot cannot give you the flu; it contains inactivated killed viruses. Adults over 49, pregnant women and those with chronic medical conditions should not receive the influenza nasal spray vaccine.

Tetanus, diphtheria and pertussis, or Tdap, is a combination vaccine with a booster given every 10 years. Tetanus is a severe and often fatal disease caused by bacteria that are widely distributed in soil, street dust and animal waste. The bacteria are very resistant to heat and germ-killing cleaners; infection can only be prevented by vaccination.

Diphtheria produces a poisonous toxin that frequently causes heart and nerve problems. Symptoms include fever, weakness and breathing problems. Although diphtheria is rare in the United States, it is common in other parts of the world and is still a threat.

Pertussis is on the rise. It is a severe illness in which prolonged coughing spells make it difficult to eat, drink and breathe; patients often lose weight and become dehydrated from vomiting. In infants, it can cause pneumonia, brain damage, seizures and mental retardation. In the elderly, it can cause pneumonia and lead to death.

Shingles is a painful, blistering skin rash caused by the chicken pox virus. If you have had chicken pox, the virus remains inactive in certain nerves; years later, the virus can become active and cause shingles. The shingles vaccine Zostavax is different from the chicken pox vaccine and is recommended for people over 60.

Pneumococcal disease is a leading cause of serious illness in children and adults throughout the world. The bacterium attacks different parts of the body. In the lungs, it causes bacterial pneumonia; in the bloodstream, it causes bacteremia; and in the covering of the brain, it causes meningitis. People ages 19–64 need one to two doses of the vaccine if they smoke cigarettes or have certain chronic medical conditions. You will need a dose at age 65 if you have never been vaccinated.

Human papillomavirus is the most common sexually transmitted virus in the United States, affecting 50 percent of sexually active people. It can cause genital warts in men and women, cervical cancer and anal and penile cancers. The vaccine Gardasil is given in three doses over six months to women age 26 or younger and can be given to men age 26 or younger to prevent genital warts.

Hepatitis A causes inflammation of the liver, contracted by consuming food or water contaminated by feces containing the hepatitis A virus or by coming in contact with the stool or blood of a person who has the disease. International travel, especially to Asia or South or Central America, places you at risk. The vaccine is given in two doses, six to 18 months apart.

Hepatitis B is an inflammation of the liver due to infection with the hepatitis B virus, which is spread through contact with the blood, semen, vaginal fluids and other body fluids of someone who is infected. The vaccine is given in three doses over six months.

Chicken pox is one of the classic viral childhood diseases, causing hundreds of itchy, fluid-filled blisters. The varicella zoster virus is a member of the herpes virus family. If you never had chicken pox or were vaccinated with only one dose, talk to your doctor about your need for the vaccine.

Measles, mumps and rubella are serious diseases. Measles causes rash, cough, runny nose, eye irritation and fever and can lead to ear infection, pneumonia, seizures, brain damage and death. The mumps virus causes fever, headache and swollen glands and can lead to deafness, meningitis, painful swelling of the testicles or ovaries and, rarely, death. The rubella (German measles) virus causes rash, mild fever and arthritis. Rubella during pregnancy can lead to miscarriage or serious birth defects. People ages 19–49 need at least one dose of the MMR vaccine.

Take the CDC’s online vaccination needs quiz (www2a.cdc .gov/nip/adultImmsched) to get a list of vaccines you need to discuss with your health care provider.

The content of this article is for informational purposes only. It is not intended to be a substitute for professional medical advice, diagnosis or treatment. Always seek the advice of your physician or other qualified health care provider with any questions you may have regarding a medical condition.