At least 922 children and young adults have died of measles in Madagascar since October, despite a huge emergency vaccination program, the World Health Organization (WHO) said on Thursday.

The number of deaths is based on official numbers, but these are likely to be very incomplete, as is the current total of infections, at 66,000, Dr Katrina Kretsinger of WHO’s expanded program on immunization told a news briefing.

Measles is a highly contagious viral disease that can cause complications including blindness and brain swelling and increase susceptibility to other diseases.

The Indian Ocean island is among Africa’s poorest countries, and in 2017 only 58 per cent of the population had been vaccinated against measles. The lack of a big outbreak since 2003 also means many have had no chance to develop immunity.

An emergency response has vaccinated 2.2 million of the 26 million population so far, Dr Kretsinger said. Some of those had previously been vaccinated but had only received one shot, and so were given the more standard second, “booster” jab.