The silent nature of the disease makes it difficult to know who in fact is infected, and therefore, from whom you could catch the virus. The presence of virus in saliva makes even simple contact with a hand towel or toothbrush, for instance, a possible means of transmission. In 1989 the United States started requiring two doses of the measles vaccine due to severe outbreaks of measles that occurred in high schools and college campuses around that time. Adults born on or before 1956 should consider themselves very likely to have been infected with measles, mumps, and rubella, and, therefore, do not need the MMR vaccine. A. Adults likely to have been infected by natural measles virus are those born before 1956.
Data also indicate that tetanus, in particular, tends to infect more people as they age.
Although the incidence of diphtheria in the United States has gone down dramatically since the 1920s, the disease still exists in the rest of the world. For example, Russia has been fighting a major epidemic of diphtheria over the last decade. As you would expect, most cases of diphtheria occur in people who have not been vaccinated. Because the United States has a high rate of business, tourist, and immigrant travel to and from countries with high rates of diphtheria infection, it remains important to be vaccinated with diphtheria vaccine. It used to be that all adults greater than 65 years of age were recommended to receive the influenza vaccine.