A double dose of reality Mixing vaccine brands and getting an mRNA booster after 2 Sinovac jabs has led to a scramble published : 12 Jul 2021 at 04:30 A health worker prepares a dose of the Covid-19 vaccine at Bang Sue Grand Station. Nutthawat Wicheanbut The threat of a prolonged Covid-19 outbreak, triggered by the Delta variant, has prompted people to scramble for alternative vaccines, including Moderna, that are not provided the state mass inoculation scheme. A mix of different types of vaccines to boost immunity against variants has increasingly become part of the decision to receive jabs amid ongoing concern about a vaccine shortage.