The potential impact of a recent measles epidemic on COVID-19 in Samoa

BackgroundThe pandemic of COVID-19 has occurred close on the heels of a global resurgence of measles. In 2019, an unprecedented epidemic of measles affected Samoa, requiring a state of emergency to be declared. Measles causes an immune amnesia which can persist for over 2years after acute infection and increases the risk of a range of other infections.MethodsWe modelled the potential impact of measles-induced immune amnesia on a COVID-19 epidemic in Samoa using data on measles incidence in 2018-2019, population data and a hypothetical COVID-19 epidemic.ResultsThe young population structure and contact matrix in Samoa results in the most transmission occurring in young people <20years old. The highest rate of death is the 60+ years old, but a smaller peak in death may occur in younger people, with more than 15% of total deaths in the age group under 20years old. Measles induced immune amnesia could increase the total number of cases by 8% and deaths by more than 2%.ConclusionsSamoa, which had large measles epidemics in 2019-2020 should focus on rapidly achieving high rates of measles vaccination and enhanced surveillance for COVID-19, as the impact may be more severe due to measles-induced immune paresis. This applies to other severely measles-affected countries in the Pacific, Europe and elsewhere.