CLINICAL QUESTION

Are vaccines for measles, mumps, rubella (MMR) and varicella effective and safe when given to children and adolescents?

EVIDENCE-BASED ANSWER

Vaccination reduces the number of cases of MMR and varicella among children and adolescents. Common adverse effects include rash and seizures, with no evidence of any increased risk of autism spectrum disorder or inflammatory bowel disease.¹ (Strength of Recommendation: A, consistent, good-quality, patient-oriented evidence.)

PRACTICE POINTERS

Vaccinations are important for reducing morbidity and mortality from infectious diseases. According to data published in 2024 by the Centers for Disease Control and Prevention (CDC), vaccine coverage (ie, the percentage of a specified population that has received a vaccine) for children younger than 3 years is 93% for the varicella and MMR vaccines; coverage among adolescents ages 13 to 15 years is 92% for varicella, and coverage among adolescents ages 13 to 17 years is 91% for MMR.² However, people decline vaccination for a variety of reasons, which can reduce population or herd immunity against some vaccine-preventable diseases.³ Hesitancy toward childhood vaccines, such as the MMR vaccine, is more common among parents with at least a college degree who prefer social media antivaccine narratives over evidence-based vaccine information.³

This is the third update of this Cochrane review, in which the authors sought to evaluate the effectiveness and safety of the trivalent MMR vaccine, concurrent administration of the MMR and varicella vaccines, or a tetravalent vaccine containing live, attenuated MMR and varicella in patients up to age 15 years.¹

This review included 138 studies (with 86 new studies); 51 studies evaluated vaccine effectiveness (47 new studies), and 87 studies evaluated vaccine safety (39 new studies).¹ Nine studies were randomized controlled trials (RCTs); the remainder were cohort, case-control, case-series, or ecological studies. The comparators were unvaccinated individuals. Four broad analyses were performed, one for each virus. The studies in this review included data from Africa, Asia, Australia, Europe, and North and South America.

Several clinical and laboratory parameters were used to evaluate the effectiveness of the vaccine against measles.¹ Individuals who received two doses of vaccine were less likely to contract measles (relative risk [RR] = 0.04; 95% CI, 0.01 to 0.28; moderate-certainty evidence). [corrected]

The most studied form of mumps vaccine was for the Jeryl Lynn strain; this live, attenuated vaccine is the most commonly used in the United States.¹ Individuals who received two doses of vaccine were less likely to develop mumps (RR = 0.12; 95% CI, 0.04 to 0.35; moderate-certainty evidence). [corrected] Household contacts of those who received a mumps vaccine were also less likely to develop mumps (RR = 0.26; 95% CI, 0.13 to 0.49; moderate-certainty evidence). [corrected]

Based on moderate-certainty evidence, rubella vaccination reduced the number of secondary cases of rubella (RR = 0.11; 95% CI, 0.03 to 0.42). [corrected]

Two doses of varicella vaccine reduced rates of varicella of any severity (rate ratio = 0.05; 95% CI, 0.04 to 0.06) over 10 years of follow-up (high-certainty evidence). [corrected]

The only short-term adverse effects associated with vaccination were increased risk of rash (RR = 2.05; 95% CI, 1.21–3.48; high-certainty evidence), and an increased risk of seizure within 1 week of MMR vaccination (rate ratio = 2.45; 95% CI, 2.21–2.71; moderate-certainty evidence).¹ There was an increased risk of idiopathic thrombocytopenic purpura after MMR vaccination (rate ratio = 4.21; 95% CI, 2.28–7.78; moderate-certainty evidence) but no evidence of an increased risk of autism spectrum disorder or inflammatory bowel disease (moderate-certainty evidence).

According to the CDC, when parents are hesitant to vaccinate a child, the clinician should listen and seek to understand the context behind parental questions.⁴ Evidence and educational resources can be helpful in addressing parental concerns.^3–5 Data from this Cochrane review can help inform such discussions.

The practice recommendations in this activity are available at https://www.cochrane.org/CD004407.