Editor’s note:This is the last of three articles on the safety of measles vaccine. Read the first two articles at https://www.aappublications.org/news/2019/04/19/measles041919 and https://www.aappublications.org/news/2019/05/14/idsnapshot051419
Immunity to measles can be acquired in one of two ways: immunization with a measles vaccine or infection by natural (wild type) measles.
Complications occur in 20% or more of people who contract measles. The more common complications associated with measles infection in a normal host are diarrhea (8%), otitis media (7%), pneumonia (6%), acute encephalitis (2 cases per 1,000 measles cases), subacute sclerosing panencephalitis (SSPE) (0.2 to 0.7 cases per 1,000 measles cases) and death (2 cases per 1,000 measles cases).
Complications of measles are most common among children younger than 5 years of age and adults 20 years of age and older.
Which of the following statements are true?
a) Complications from a measles infection are likely to be present if the fever has not lysed within one to two days after rash onset.
b) In the U.S., the measles case-fatality rate may be as high as 50% in children infected with HIV.
c) Measles infection during pregnancy results in an increased risk of premature labor, spontaneous abortion and an infant with low birthweight.
d) Pneumonia may be viral or bacterial and is the most common cause of measles-related death in children
e) Rates of SSPE in the U.S. fell from 0.6 cases/million people in 1963 to 0.01 cases/million people in 1997, following licensure of the measles vaccine.
f) Vitamin A administration is not recommended for U.S. children who are hospitalized due to measles infection.
Answer: a, b, c, d and e are true
The safety and effectiveness of the live attenuated measles vaccine is without question. The suggestion of a potential link between the measles vaccine and autism has been reviewed thoroughly by governmental groups as well as nongovernmental groups, including the Academy. All reviews independently have concluded that no scientifically rigorous or reproducible evidence exists to support a potential link between the measles, mumps, rubella (MMR) vaccine and autism.
One of the largest studies regarding measles vaccine and autism evaluated more than 650,000 Danish children born between 1999 and 2010 and determined no difference in the risk of autism between children vaccinated with MMR and children who did not receive the vaccine (Hviid A, et al. Ann Intern Med. 2019;170:513-520). The authors determined there was no increased risk for autism in vaccinated children with a sibling history of autism.
Despite multiple, scientifically rigorous studies that have found no link between MMR vaccine and autism, the myth of an association has persisted.
Pregnant women infected with measles are more likely to be hospitalized, develop pneumonia and die than nonpregnant infected women. Clinical illness in the newborn after intrauterine exposure varies from mild to severe and can be fatal. There is no convincing evidence that maternal infection with measles during pregnancy is associated with specific congenital malformations.
Vitamin A treatment of children with measles in resource-limited countries is associated with decreased morbidity and mortality rates. Lower serum concentrations of vitamin A have been found in U.S. children with more severe measles. Even in developed countries, vitamin A should be administered to all children with severe measles (see 2018 Red Book, page 541 for dosing).
In addition, vitamin A therapy should be administered to children with measles who are immunosuppressed, have clinical evidence of vitamin A deficiency or recently immigrated from areas with a high mortality rate from measles. Parenteral and oral formulations of vitamin A are available in the U.S.
Following acute measles virus infection, a persistent infection with a defective measles virus in the central nervous system may occur causing SSPE. A degenerative central nervous system disease, SSPE is characterized by behavioral changes, intellectual, mental and motor deterioration, seizures and death. Once symptoms start, a child or adolescent with SSPE experiences progressive personality changes, myoclonic seizures, motor disability and coma, and dies one to three years after symptom onset. The live attenuated measles vaccine strain does not cause SSPE.
The previous estimate of one SSPE case per 100,000 natural measles cases now is considered to be an underestimation. During the resurgence of measles in the U.S. during 1989-’91, the overall occurrence of SSPE among children in California was estimated to be 20/100,000 reported measles cases. The risk of SSPE among children younger than 5 years at the time of infection was estimated to be as high as 75/100,000 reported measles cases and for children younger than 12 months, the risk is estimated at 160/100,000 reported measles cases.
The pathogenesis of SSPE is thought to be a slow virus infection that occurs after the wild type measles virus enters the brain during the acute primary infection and then persists in the nervous system. Measles virus from a child with SSPE is not transmitted to others. SSPE has largely disappeared in countries where measles control has been achieved through use of the measles vaccine.
An under-recognized benefit of measles vaccination is the reduction in all-cause childhood mortality (non-specific effect) that occurs following initiation of a vaccine program. By preventing a measles infection, vaccination prevents the undesirable short- and long-term immunomodulating effects that follow an acute case of measles. Vaccination reduces the months or years of increased susceptibility to non-measles morbidity and mortality that predictably follows wild type measles infection.
Dr. Meissner is professor of pediatrics at Floating Hospital for Children, Tufts Medical Center. He also is an ex officio member of the AAP Committee on Infectious Diseases and associate editor of the AAP Visual Red Book.