A recent study has shown that the protection provided by the measles vaccine can slowly decrease over time, leading to an increase in cases of the contagious disease among both unvaccinated and double-vaccinated individuals, particularly children under the age of 10. The research, published in The Lancet Public Health, indicates that over 95% of people who have received two doses of the measles, mumps and rubella (MMR) vaccine, introduced in 1988, are protected for life.
The UK Health Security Agency (UKHSA) has reported that the majority of measles cases in England occur in unvaccinated children and young people, but there has been a rise in infections among those who have received both doses of the vaccine. A modelling study conducted by The London School of Hygiene & Tropical Medicine (LSHTM) suggests that the effectiveness of the MMR vaccine can gradually decrease by 0.04% each year after the second dose, leading to breakthrough cases of measles in vaccinated individuals.
Experts emphasize that the slight decrease in vaccine immunity is primarily due to lower vaccination coverage compared to the 95% target set by the World Health Organisation (WHO). The findings suggest that maintaining high vaccination coverage is essential to prevent measles transmission and outbreaks in communities. Currently, only 85% of under-fives in England have received two doses of the MMR vaccine.
Dr. Alexis Robert, a research fellow at LSHTM, highlighted that before routine measles vaccination, England and Wales experienced large outbreaks with up to 600,000 cases in some years. However, the introduction of the MMR vaccine has significantly reduced the number of reported cases. While some cases of measles in double-vaccinated individuals have been observed, the overall effectiveness and safety of the MMR vaccine remain unquestioned.
The study also explored scenarios using mathematical modelling to understand the increase in measles cases among adults who have received two doses of the MMR vaccine. Results indicated that slow waning of vaccine immunity aligns with the distribution of cases over time and by age group. Dr. Vanessa Saliba, a consultant epidemiologist at UKHSA, reiterated the importance of maintaining high vaccination rates to achieve global measles elimination.
In conclusion, the research underscores the critical role of vaccination in preventing measles outbreaks. While some waning in vaccine immunity may occur over time, the MMR vaccine continues to offer substantial protection against measles. Parents are encouraged to ensure their children are up to date with vaccinations to safeguard against this highly contagious disease.