In the week of World AIDS Day, Health Check looks at what's being described as a milestone in the prevention of HIV infection in women. It is a form of pre-exposure prophylaxis (PrEP) - an injection every 8 weeks of a drug called cabotegravir. A clinical trial has been comparing it to a daily PrEP pill which is already known to be effective at preventing HIV infection. The injection regimen was about 90% more effective at shielding women from the virus than the daily tablet. The trial involves more than 3,000 women in seven Southern and East African countries. Claudia talks to study co-leader Sinead Delany-Moretlwe of the University of Witwatersrand about why this form of PrEP seems to be so effective and whether it will be affordable for low and middle income countries. Chhavi Sachdev reports on informal health workers known as ‘chhota doctors’ who are the backbone of primary health care for the hundreds of millions of rural people in India. They are not formally recognised as health care providers by the authorities and lack medical degrees, but they are the first port of call for many when people feel ill, particularly during India’s coronavirus lockdown. At a time when so many people are stuck indoors working at home, World Health Organisation has published new recommendations on how much physical activity we should be doing for the sake of our health. We talk to Fiona Bull, head of the WHO’s physical activity unit. James Gallagher is the Health Check guest this week talking about Covid-19 vaccines, vitamin D and a step towards a blood test to predict Alzheimer’s disease. Presenter: Claudia Hammond Producer: Andrew Luck-Baker (Picture: Female doctor giving a young female patient an injection in her consultation room. Photo credit: Henk Badenhorst/Getty Images.)