MONDAY, Sept. 30, 2024 (HealthDay News) — Measles cases in England are consistent with the waning of vaccine-induced immunity, according to a study published online Sept. 26 in The Lancet Public Health.
Alexis Robert, Ph.D., from the London School of Hygiene & Tropical Medicine, and colleagues examined whether measles dynamics observed in England between 2010 and 2019 were in line with waning of vaccine-induced immunity using a compartmental mathematical model stratified by age group, region, and vaccine status. The deterministic model was fitted under three scenarios: without waning of vaccine-induced immunity, with waning depending on time since vaccination, and with waning depending on time since vaccination starting in 2000.
The researchers found that the number of one-dose recipients among measles cases was overestimated in the scenario without waning, and the number of two-dose recipients was underestimated among cases older than 15 years (median, 75 cases in simulations without waning; 196 cases in simulations with waning; 188 cases in simulations when waning started in 2000; and 202 observed cases). The number of onward transmissions from vaccinated cases was 83 percent of transmissions from unvaccinated cases. There was a slow estimated waning rate (0.039 percent per year of age), but this was sufficient to increase the burden of measles.
“The waning of vaccine-induced immunity likely explains the observed dynamics and age distribution of vaccinated measles cases in England between 2010 and 2019,” the authors write. “Many near-elimination countries have reported decreased vaccine coverage since 2020, leading to an increase in measles incidence in Europe in 2023.”
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