Measles Vaccines Reported Safe Once Again

A new review of the existing evidence on the safety and effectiveness of measles-related vaccines supports their continued use for mass immunization around the world.

This conclusion published on April 20, 2020, is based on a substantive, worldwide Cochrane Systematic Review of the MMR (measles, mumps, rubella) vaccine that protects against all three infections. 

Additional measles vaccine configurations include varicella (chickenpox) by a combined MMR and varicella vaccine (MMRV) or giving it separately at the same time (MMR+V). 

"We wanted to assess the effectiveness, safety, and long- and short-term harms of the MMR vaccines in this updated review, which was last updated in 2012," explained lead author, Dr. Carlo Di Pietrantonj of Italy's Regional Epidemiology Unit SeREMI, in a related press release.

"From the 138 randomized and non-randomized studies included in the review, 51 studies (10 million children) assessed how effective the vaccines were at preventing the diseases, and 87 studies (13 million children) assessed harms."

In terms of effectiveness this review found:

• Measles: one dose of vaccine was 95% effective in preventing measles. Based on the data analyzed in the review, the number of cases would fall from 7% in unvaccinated children to under 0.5% in children who receive one dose of the vaccine. After two doses, effectiveness was similar at around 96%.
• Mumps: One dose of vaccine was 72% effective in preventing mumps. This rose to 86% after two doses. From data analyzed in the review. the number of cases would fall from 7.4% in unvaccinated children to 1% in children who were vaccinated with two doses.
• The results for rubella and chickenpox also showed that those vaccines are effective. After one dose of vaccine was 89% effective in preventing rubella.
• One study found that after 10 years the MMRV vaccine was 95% effective at preventing chickenpox infection. If exposed to chickenpox, 5 out of 100 vaccinated children would catch it.

"In terms of safety, we know from previous studies all around the world that the risks posed by these diseases far outweigh those of the vaccines administered to prevent them," says Dr. Di Pietrantonj.

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"In this review, we wanted to look at the evidence for specific harms that have been linked with these vaccines in public debate - often without rigorous scientific evidence as a basis."

In relation to the controversy arising from false claims linking vaccination and autism, the review summarises evidence from studies with 1,194,764 children. 

These studies found diagnosed cases of autism were similar in vaccinated and unvaccinated children.

Two further studies with 1,071,088 children find no evidence for any association between the MMR vaccines and encephalitis, inflammatory bowel disease, Crohn's disease, cognitive delay, type 1 diabetes, asthma, dermatitis/eczema, hay fever, leukemia, multiple sclerosis, gait disturbance, and bacterial or viral infections.

“Although the studies that provide these data are not randomized the effects are very large. The certainty of the evidence for the varicella vaccine, based on an RCT, was judged to be high," says Di Pietrantonj.

"Overall we think that existing evidence on the safety and effectiveness of MMR/MMRV/MMR+V vaccines supports their use for mass immunization.” 

“Campaigns aimed at global eradication should assess epidemiological and socioeconomic situations of the countries as well as the capacity to achieve high vaccination coverage.” 

“More evidence is needed to assess whether the protective effect of MMR/MMRV could wane with time since immunization."

For this 2019 update, the review authors gratefully acknowledge help received from Liz Dooley, Ann Jones, Janet Wale, David Elliman, Jenny Doust, Kerry Dwan, Tess Moore, Andrew Anglemyer, and Liz Bickerdike. This 2019 update was funded by the UK's National Institute for Health Research (NIHR) Cochrane Incentive Scheme.

No industry conflicts were disclosed. 

MMR vaccine news published by Precision Vaccinations.