Measles Outbreaks can Occur among Highly MMR vaxxed populations
With measles in the news after a documented 124 cases in the U.S. it should be remembered that measles outbreaks can still happen even in populations with so-called herd immunity as a result of primary or secondary vaccine failure. There are several recorded instances of measles outbreaks occurring in nearly universally MMR vaxxed populations throughout the U.S. here are some examples:
1985 outbreak in Corpus Christi, Texas despite 99% of student body being vaxxed
Source: New England Journal of Medicine
1985 outbreak in Browning, Montana despite 98.7% of student body being vaxxed
Source: American Journal of Epidemiology
1985 outbreak in an Illinois high school despite 99.7% of the student body being vaxxed
Source: American Journal of Epidemiology
1988 outbreak at a college in Colorado despite 98% of the student body being vaxxed:
70/84 cases occurred in students with prior documentation of measles immunization in early childhood.
Source: American Journal of Public Health
1989 outbreak in Quebec City; despite 99% of the population being vaxxed:
85% of measles cases were previously immunized against measles
Source: Canadian Journal of Public Health
1992 outbreak in Capetown, SA despite 91% of the student body being vaxxed
Source: South African Medical Journal
Misdiagnosis of atypical measles in MMR vaxxed patients
Even while measles outbreaks have been declining for decades similar diseases with similar clinical presentations seemingly took its place.
A 1979 case series study published in The American Journal of Public Health found that atypical measles in vaxxed adolescents and children was only correctly diagnosed in 17 out of 56 patients, 42 of whom had been hospitalized. The article below presents 2 more cases of adolescents who were diagnosed with the measles despite MMR immunization earlier in childhood.
Delayed diagnosis in atypical measles syndrome
Another case study of atypical measles in an adult patient that visited India notes that ‘atypical measles may be misdiagnosed as varicella, Rocky Mountain spotted fever, toxic shock syndrome, or drug eruption’ and estimate that primary or secondary MMR immunization failure can occur in 5% of patients.
Cases diagnosed as Rocky Mountain Spotty Fever began rising just as measles cases were on the decline. Rocky Mountain Spotty Fever has similar clinical presentation to measles, infectious mono-nucleosis, and chickenpox. A 5 year case series study conducted between 1970 and 1974 (n = 63) notes that several patients initially diagnosed with rocky mountain spotty fever were subsequently diagnosed with atypical measles. All of these patients had been immunized against measles in the past. Two patients initially diagnosed with the measles turned out to have RMSF instead.
Incidents of Rocky Mountain Spotty feverhad precipitously risen in the U.S. since the introduction of measles immunizations in the early 1960s, especially between 1964 and 1981 and again between 2000 and 2017.
Kawasaki Disease also has a similar clinical presentation to measles and other viral exanthem infections. A retrospective cohort study of pediatric patients hospitalized for suspected measles cases during an outbreak in Chicago (n = 48) found that 6 patients fit the CDC criteria for Kawasaki disease. Ultimately, 3 were diagnosed and treated for Kawasaki disease and 3 were diagnosed and treated for measles and 2 patients were diagnosed with toxic shock syndrome.
A case study of atypical measles in a 22 year old man notes that differential diagnosis of atypical measles includes Rocky Mountain spotty fever and Kawasaki disease.
Another case study of atypical measles in a 14 year old boy notes that Kawasaki syndrome and atypical measles are two possible diagnoses based on the clinical presentation of the boy’s illness.
An epidemiological study of Kawasaki Disease prevalence in the U.S. utilizing 10 years (1988-97) of Nationwide Inpatient Sampling Data on hospital discharges of pediatric patients across 22 states (n = 6,442) found that the incidence of this disease more than doubled for Children under 5 years of age from 8.1 hospitalizations per 100,000 children in 1988 to 18.5 hospitalizations per 100,000 children in 1997. The incidence of this disease also more than doubled for children under 10 years of age from 5 hospitalizations per 100,000 children in 1988 to 11.7 hospitalizations per 100,000 children in 1997. Kawasaki Disease was more common in males than females by a ratio of 3 to 2 for children less than 10 years of age and 3 to 1 for children 10 years of age or older. Like measles, Kawasaki disease cases peaked in the winter and declined during the spring and summer.