According to US experts, booster vaccinations should be given to vulnerable individuals — including hospital and care home workers — first, then the public.

Research has indicated that it stops severe inflammation, or sepsis — without presenting any risk of side effects.

'Vaccination with the MMR jab may be especially beneficial for health care workers who might easily be exposed to COVID-19,' said paper author and immunologist Paul Fidel of the Louisiana State University.

'Live attenuated vaccines seemingly have some non-specific benefits as well as immunity to the target pathogen,' Dr Fidel explained.

'A clinical trial with MMR in high-risk populations may provide a low-risk, high-reward preventive measure in saving lives during the pandemic.' 

Recent events have provided indications that the hypothesis might be applicable in practice, Dr Fidel said. 

In the US Navy, the MMR jab is given to all recruits — and in an outbreak among the crew of the aircraft carrier the USS Roosevelt, milder symptoms were seen in 955 of the sailors who tested positive for COVID-19, with only one needing hospitalisation.