Public health in London, Ont., is asking residents to choose the Moderna COVID-19 vaccine before thousands of doses expire.

       The Middlesex-London Health Unit says more than 21,300 doses of the mRNA shot have been thawed and need to be used by Aug. 12.

       It says vaccinations have declined over the last two weeks and the available Moderna shots are “above and beyond” shots already allocated for second doses.

       The region’s top doctor is asking people who visit clinics for their shots in the next two weeks to take the Moderna vaccine and help avoid wastage.

       Ontario and other Canadian provinces have been offering Moderna shots after a first dose of Pfizer and vice-versa in order to quickly vaccinate as many people as possible.

       The London health unit says mRNA interchangeability is at “the foundation of its vaccination program” and says they can be mixed without concern.

       Facebook's new video series, Let Me Explain, discusses various topics related to safety and integrity on its platforms. Supplied by Facebook

       Sign up for the Coronavirus Update newsletter to read the day’s essential coronavirus news, features and explainers written by Globe reporters and editors.