What’s behind the return of monkeypox?

27 May 2022

C Raina MacIntyre, Professor of Global Biosecurity at UNSW, writes about the recent monkeypox outbreak, which may be linked to the discontinuation of vaccine programs for the now eradicated smallpox virus, an immunisation that also offered protection from monkeypox.

Scientists have puzzled over why a previously rare infection is now becoming more common. The vaccine against smallpox also protects against monkeypox, so in the past, mass vaccination against smallpox protected people from monkeypox too. It is 40 years since smallpox was declared eradicated, and most mass vaccination programs ceased in the 1970s, so few people aged under 50 have been vaccinated. There are even fewer in Australia, where mass smallpox vaccination was never used, and an estimated 10% of Australians have been vaccinated. The vaccine gives immunity for anything from five to 20 years or more, but may wane at a rate of about 1-2% a year.