The Centers for Disease Control and Prevention (CDC) states that, prior to the introduction of the first measles vaccine in the United States in 1963, it had been receiving nearly 500,000 reported cases of measles each year.1 2 3 4 That number is correct if you average the total number of measles cases reported during 1958-1962. The average comes to 503,282 cases annually.4 5 6
The picture looks a lot different, however, if you delete from the equation the year 1958. If you take the measles cases reported during 1959-1962, the annual average comes out to 438,3285 6—or almost 20,000 less than the measles cases reported to the CDC the year after the measles vaccine was introduced in the U.S. The CDC received 406,162 reported cases of measles in 1959; 441,703 in 1960; 423,919 in 1961; and 481,530 in 1962.5 6 It received 385,156 reported cases of measles in 1963 and 458,083 in 1964. This is worth noting because it is often pointed out that after the measles vaccine was introduced, the incidence of measles plummeted.
According to a 1992 paper written by Jacqueline Gindler, William Atkinson and Lauri Markowitz in the journal Epidemiologic Reviews:
Following the introduction and widespread use of measles vaccines, measles incidence declined dramatically.4
The impression given here is that the decline was sharp and immediate. Not quite. The dramatic decline in the number of reported measles cases occurred in 1965 when they dropped to 261,904, followed by 204, 136 in 1966; 62,705 in 1967; 22, 231 in 1968; and 25,826 in 1969.
“By 1978, the number of reported cases had decreased by almost 95 percent compared with the prevaccine era,” wrote Gindler, Atkinson and Markowitz.4
There is no question that 95 percent decrease represents a marked decline in reported cases of measles in the U.S. during that period. It is interesting, though, that the reported decline in measles cases correlates with other reported declines occurring in the U.S. population at that time, including a significant decline in birth rates between 1965-1969. For the first time since World War II ended in 1945, there were less than 20 live births per 1,000 people in the U.S. The birth period for the so-called “Baby Boomer” generation had come to an end. There were far fewer babies being born beginning in 1965 than in each of the previous 20 years.7 8
In 1965, there were a total of 3,760,358 live births in the U.S., compared to 4,027,490 in 1964. That’s 267,132 fewer American babies in that year’s birth cohort. If you compare 1965 to 1957, a year when the Baby Boomer birth rate hit its peak at 25.3 live births per 1,000 (for a total of 4,308,000 live births), the difference is 547,642 fewer American babies born in 1965. That peak birth rate in 1957 may have had something to do with the 763,094 reported cases of measles in 19585 6 7—the peak annual number for measles cases recorded in the 1950s.
Live births in the U.S. steadily declined after 1957 to 24.5 per 1,000 in 1958; 24.3 in 1959; 23.7 in 1960; 23.3 in 1961; 22.4 in 1962; 21.7 in 1963; 21.0 in 1964 and 19.4 in 1965. The rates kept dropping throughout the rest of the 1960s and the 1970s when they leveled off at 14.8 in both 1975 and 1976, and they have remained under 17 ever since—mostly under 16.
Is it possible that significant and consistent declines in U.S. birth rates after 1957 were at least a co-factor in the significant and consistent declines in reported measles cases beginning in 1965?
2 CDC. Measles Data and Statistics. CDC.gov Feb. 16, 2018 (last updated).
3 CDC. Measles Data and Statistics. CDC.gov Feb. 16, 2018 (last updated).
4 Gindler JS, Atkinson WL, Markowitz LE. Update—The United States Measles Epidemic, 1980-1990. Epidemiologic Reviews 1992.
5 Cáceres M. The Story of Measles’ Sharp Decline. The Vaccine Reaction Apr. 12, 2016.
6 CDC. Summary of Notifiable Diseases, United States: 1989. Morbidity and Mortality Weekly Report Oct. 5, 1990; 38(54):56-58.
7 Live Births and Birth Rates, by Year. Infoplease.com.
8 Baby Boomer. Investopedia.com.