Risk Factors for Measles Nonimmunity in Rubella-Immune Pregnant Patients
Elias Kassir1, Kerry Holliman1, Masaru Negi1
1Department of Obstetrics and Gynecology, University of California, Los Angeles (UCLA), Los Angeles, California.
Objective:
Measles immunity testing, unlike that for rubella, is not currently part of prenatal screening even though immunity to both is conferred by the measles-mumps-rubella (MMR) vaccine. Although endemic transmission of measles was declared eliminated in the United States in 2001, outbreaks have continued to occur. Given the risks associated with measles infection during pregnancy, we sought to identify risk factors for measles nonimmunity (MNI) in rubella-immune (RI) pregnant individuals.
Methods:
We performed a retrospective observational cross-sectional study of patients receiving prenatal care and delivering at two university hospitals and a county hospital in Southern California from April 1, 2019 to February 1, 2021. Inclusion criteria were pregnant individuals ≥18 years old who had serological testing for rubella and measles during pregnancy. Demographic data were extracted from electronic medical records, including results of serological testing and chronic medical conditions. All subjects were rubella immune, and we compared measles-immune (MI) with MNI groups.
Results:
In total, 1,813 RI individuals were identified, with 1,467 (81%) MI and 346 (19%) MNI individuals. Variables associated with an increased risk of MNI included having public health insurance (adjusted relative risk [aRR]: 1.56; 95% confidence interval [CI]: 1.24, 1.97) and Hispanic ethnicity (aRR: 1.37; 95% CI: 1.06, 1.78). Black race was associated with a decreased risk of MNI (aRR: 0.52; 95% CI: 0.29, 0.91). Birth year before 1989 demonstrated a trend toward increased risk of MNI, but this did not reach statistical significance (aRR 1.23; 95% CI: 1.00, 1.52). No differences were seen between the two groups for medical comorbidities.
Conclusion:
Our study is the first to demonstrate risk factors for measles MNI in patients with documented rubella immunity. In the absence of universal measles serological screening recommendations, the risk factors identified could help guide clinicians in selective screening for those at risk of needing postpartum MMR vaccination.
Key Points:
· The rate of measles nonimmunity is higher than previously reported.. · Hispanic ethnicity and use of public insurance are risk factors for measles nonimmunity.. · The current recommendation for history-based screening for measles immunity is likely insufficient..
Insights
Measles nonimmunity is more common than expected in pregnant individuals, with Hispanic ethnicity and public insurance increasing risk. This highlights the need for improved screening beyond medical history for measles immunity.
Area of Science:
- Public Health
- Infectious Diseases
- Obstetrics & Gynecology
Background:
- Measles-mumps-rubella (MMR) vaccination confers immunity to both measles and rubella.
- Prenatal screening for measles immunity is not standard practice in the US, despite ongoing measles outbreaks.
- Measles infection during pregnancy poses significant risks.
Purpose of the Study:
- To identify risk factors for measles nonimmunity (MNI) among rubella-immune (RI) pregnant individuals.
- To inform targeted screening strategies for measles immunity in pregnant populations.
Main Methods:
- Retrospective observational cross-sectional study.
- Inclusion of pregnant individuals (≥18 years) with serological testing for rubella and measles.
- Analysis of demographic data and chronic medical conditions from electronic health records.
Main Results:
- 19% of rubella-immune pregnant individuals (346/1813) had measles nonimmunity.
- Increased risk of MNI associated with public health insurance (aRR: 1.56) and Hispanic ethnicity (aRR: 1.37).
- Black race showed a decreased risk of MNI (aRR: 0.52).
Conclusions:
- This study identifies key demographic risk factors for measles nonimmunity in pregnant individuals.
- Current history-based screening for measles immunity is likely insufficient.
- Findings can guide clinicians in selective screening for measles immunity and postpartum vaccination needs.
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