Although the coronavirus vaccine is the one on most everyone’s mind these days, vaccines for at least 27 diseases are now in use in the United States, according to the Centers for Disease Control and Prevention. This includes vaccines to prevent mumps, measles, the flu, pneumonia and more. Among the available vaccines for children and adults, 17 (in addition to the one for covid-19) are on the CDC’S recommended list for protection against particularly dangerous or deadly diseases, such as polio, diphtheria, hepatitis, tetanus and whooping cough. (Neither list has been updated to include covid-19). In addition, the World Health Organization says that vaccines are now being developed to target at least 15 more diseases, including tuberculosis and malaria. A vaccine, most often given by injection (a shot), is a preparation that essentially teaches your immune system to identify and fight off harmful germs, such as viruses and bacteria, thus keeping you from getting sick. Determining which vaccines would benefit a particular person depends on such things as age (older people, for instance, are urged to get a shingles vaccine) and upcoming travel that might expose you to diseases no longer common in the United States (such as cholera). Getting a vaccine protects an individual, but when enough people are vaccinated against a particular disease, it becomes harder for that illness to spread. That helps create what is called herd immunity. It also can lead to near-eradication of a disease, which is what happened with polio in the United States. On the flip side, however, an American Heart Association survey found that 60 percent of Americans say they may delay or skip getting a flu vaccination this year, which experts say will likely lead to a bad flu season. Among other negatives, the pandemic has resulted in a worrisome drop in childhood vaccination rates.