Evaluating Scope and Bias of Population-Level Measles Serosurveys: A Systematized Review and Bias Assessment

Abstract

Background: Measles seroprevalence data have potential to be a useful tool for understanding transmission dynamics and for decision making efforts to strengthen immunization programs. In this study, we conducted a systematized review and bias assessment of all primary data on measles seroprevalence in low- and middle-income countries (as defined by World Bank 2021 income classifications) published from 1962 to 2021.

Methods: On 9 March 2022, we searched PubMed for all available data. We included studies containing primary data on measles seroprevalence and excluded studies if they were clinical trials or brief reports, from only health-care workers, suspected measles cases, or only vaccinated persons. We extracted all available information on measles seroprevalence, study design, and seroassay protocol. We conducted a bias assessment based on multiple categories and classified each study as having low, moderate, severe, or critical bias. This review was registered with PROSPERO (CRD42022326075).

Results: We identified 221 relevant studies across all World Health Organization regions, decades, and unique age ranges. The overall crude mean seroprevalence across all studies was 78.0% (SD: 19.3%), and the median seroprevalence was 84.0% (IQR: 72.8-91.7%). We classified 80 (36.2%) studies as having severe or critical overall bias. Studies from country-years with lower measles vaccine coverage or higher measles incidence had higher overall bias.

Conclusions: While many studies have substantial underlying bias, many studies still provide some insights or data that could be used to inform modelling efforts to examine measles dynamics and programmatic decisions to reduce measles susceptibility.

Keywords: bias; measles; serology; seroprevalence.

Figure 1

PRISMA diagram.

Figure 2

Number of serosurveys with data included per country. Map of the number of studies per country with available data identified by the systematized review.

Figure 3

Measles seroprevalence by time period and overall bias level. Beeswarm plot of measles seroprevalence by time period. Each point represents one country-year of data per study and is colored according to the overall bias level. The black lines represent the median observation across each decade.

Figure 4

Overall bias level by MCV1 coverage and annual measles incidence. Each point represents each country-year across all studies, the overall bias level by MCV1 coverage (top), and the annual estimated measles incidence (bottom).