Thailand is set to extend the gap between the first and second shots of AstraZeneca’s coronavirus vaccine to 16 weeks, in a bid to vaccinate more people faster, a top health official reported on Monday.

The move follows a similar decision by Spain to stretch the gap between 2 AstraZeneca shots to 16 weeks, which is beyond the 12 weeks maximum interval approved by the European Medicines Agency. A 16-week interval has not been tested in human trials.

Thailand’s change, from a 10-week gap previously, comes before the planned start of a mass immunization campaign from June, for which AstraZeneca’s vaccine will be the main one used.

Kiattiphum Wongrajit, permanent secretary of the health ministry, told Reuters: “This is to increase the number of people who get vaccinated,” noting that it would help reach herd immunity faster.

The country has since the start of April been struggling to contain a third wave of COVID-19 infections, with its latest outbreak accounting for nearly 80% of its total 132,213 cases and 806 fatalities.

Kiattiphum added that Thailand will focus on administering the first of two AstraZeneca jabs between June and September.

It previously said it aimed to inoculate 70% of its population by September to create herd immunity.

The national vaccine strategy relies almost completely on AstraZeneca vaccines, the majority of which it said would be produced by a local firm owned by the country’s king.