Although everyone is talking about the coronavirus vaccine these days, vaccines are now used against at least 27 diseases in the United States, according to the Centers for Disease Control and Prevention. These include vaccines to prevent mumps, measles, flu, pneumonia, and more. Of the vaccines available for children and adults, 17 (in addition to the Covid-19 vaccine) are on the CDC’s recommended list for protection against particularly dangerous or fatal diseases such as polio, diphtheria, hepatitis, tetanus and whooping cough. (No list has been updated to include Covid-19). In addition, according to the World Health Organization, vaccines are currently being developed for at least 15 other diseases, including tuberculosis and malaria. A vaccine, usually given by injection (shot), is a preparation that essentially teaches your immune system to recognize and fight off harmful germs such as viruses and bacteria in order to keep you safe from disease. Deciding which vaccines would benefit a particular person depends on factors such as age (the elderly are strongly advised to get shingles vaccine, for example) and upcoming trips, which may expose you to diseases that are no longer common in the United States (like cholera and smallpox). Getting a vaccination protects a person, but when enough people are vaccinated against a particular disease, it becomes more difficult for that disease to spread. This helps create what is known as herd immunity. It can also lead to near-eradication of a disease, as was the case with polio in the United States. On the flip side, however, an American Heart Association poll found that 60 percent of Americans say they may delay or skip a flu shot this year, which experts say will likely lead to a bad flu season. Among other things, the pandemic has led to a worrying decline in vaccination rates among children.