In the densely populated Lower Mainland of British Columbia, a recent serological survey has revealed a strikingly high prevalence of measles antibodies among residents, underscoring the region’s robust immunization efforts. Published in the Canadian Medical Association Journal, this population-based, cross-sectional study conducted in August 2024 analyzed blood samples from over 1,000 individuals spanning multiple age cohorts. The findings demonstrated that approximately 90% of participants possessed detectable measles antibodies, reflecting widespread immunity that is critical in maintaining community protection against this highly contagious viral infection.
Measles, caused by the Morbillivirus, remains a significant global health challenge despite the availability of a safe and effective vaccine. In North America, recent years have seen a resurgence in measles cases, with Canada reporting over 4,000 cases by August 2025 alone. This surge marks a fivefold increase in annual incidence since the country’s declaration of measles elimination in 1998. The infectious nature of measles necessitates maintaining herd immunity levels between 92% and 94% to prevent sustained outbreaks and viral transmission through populations.
The foundation of immunity in communities stems from two primary sources: natural infection and vaccine-induced protection. Individuals born prior to 1970 are largely presumed to be immune through natural exposure to endemic measles, which circulated widely before widespread immunization programs were established. Conversely, those born after this period rely almost exclusively on vaccination protocols, which in British Columbia recommend a two-dose regimen. The first dose is typically administered at 12 months of age, followed by a second dose between 4 to 6 years, ensuring a robust immune response and long-lasting seroconversion.
Recent concerns have emerged regarding the increase in vaccine hesitancy, which threatens to erode these high coverage rates. Public health officials highlight that approximately 90% of measles cases in Canada involve unvaccinated individuals, underscoring the crucial role vaccination status plays in individual and herd protection. Vaccine hesitancy, fueled by misinformation and complacency, poses a tangible risk to community immunity levels and demands ongoing public health vigilance and intervention strategies.
The study’s data revealed nuanced age-related differences in antibody prevalence. Among young children aged 2 to 3 years, seroprevalence ranged from 92% to 94%, while slightly older children aged 4 to 6 years exhibited antibody presence in 97% of cases. These numbers reflect successful uptake of both vaccine doses. However, a dip in antibody levels was detected in older children, a trend possibly influenced by pandemic-related disruptions that delayed scheduled second-dose vaccinations, thereby temporarily compromising optimal immunity in this group.
In adult populations, the sero-survey identified near-universal antibody presence in those aged 55 years or older. This cohort’s immunity likely results from natural infection in early childhood, conferring lifelong protection. Contrastingly, only about 75% of adults aged 20 to 39 years exhibited detectable measles antibodies. This discrepancy may be attributable to waning vaccine-induced immunity over time, particularly in individuals vaccinated in infancy whose maternal antibodies were diminished due to their mothers’ vaccine-derived immunity rather than natural infection.
Interestingly, individuals lacking detectable antibodies are not necessarily devoid of protection. The immune system’s complexity entails multiple arms of defense beyond circulating antibodies, including memory T cells and B cells, which can mediate rapid and effective responses upon measles virus exposure. Thus, seronegativity does not unequivocally signify susceptibility but highlights areas where enhanced surveillance and potential booster interventions could be warranted.
Dr. Danuta Skowronski and her coauthors emphasize the epidemiological context supporting these serological findings. Measles outbreaks in British Columbia and across Canada remain sporadic and self-limiting, predominantly occurring in clusters of unvaccinated individuals or tightly knit communities with lower vaccine coverage. This pattern aligns with the observed overall high levels of population immunity and suggests that current vaccination efforts are effectively suppressing sustained or generalized viral transmission.
The research also brings to light challenges related to vaccine documentation. The higher-than-expected seroprevalence in children, which exceeds some vaccination coverage estimates, suggests that administered doses may be underreported in health records. This underlines the necessity for precise and efficient immunization registries that accurately capture two-dose coverage, facilitating targeted public health actions and resource allocation for catch-up campaigns.
Periodic population-based serosurveys, such as this, provide invaluable insights beyond standard vaccination coverage metrics. By directly measuring immunological markers within the population, these surveys can detect gaps in immunity, inform catch-up vaccination strategies, and guide adjustments to immunization programs. Such adaptive measures are essential to sustain measles elimination goals and to mitigate the impact of shifting epidemiological landscapes and vaccine uptake patterns.
Moreover, the survey’s findings offer reassurance amid ongoing concerns related to vaccine hesitancy and the disruption caused by the COVID-19 pandemic. The overwhelming majority of parents demonstrate understanding and adherence to vaccination schedules, contributing to maintained herd immunity and public health security. These outcomes highlight the critical need to continue promoting vaccine acceptance and addressing misinformation to preserve the gains achieved.
The British Columbia serosurvey stands as a testament to the power of well-executed immunization programs and robust surveillance systems. Maintaining high two-dose measles vaccine coverage remains a priority to prevent outbreaks and to protect vulnerable populations. As measles continues to challenge public health coordinators globally, insights from such studies provide a roadmap for measurable progress towards sustained disease elimination.
In conclusion, this comprehensive serosurvey conducted in British Columbia illuminates the immunological landscape of measles protection across age cohorts, reinforcing the effectiveness of vaccination strategies. It also calls attention to ongoing vigilance against vaccine hesitancy, the importance of accurate immunization data capture, and the value of seroepidemiological tools in informing public health policy. The study embodies a critical step in safeguarding population health and preventing the resurgence of a disease once declared eliminated in Canada.
Subject of Research: People
Article Title: Measles seroprevalence by birth cohort across the lifespan: a population-based, cross-sectional serosurvey in British Columbia, Canada
News Publication Date: 14-Oct-2025
Web References: https://www.cmaj.ca/lookup/doi/10.1503/cmaj.250788
References: Canadian Medical Association Journal, DOI: 10.1503/cmaj.250788
Keywords: Measles, Viral infections, Immunization, Vaccination, Public health, Pediatrics
