Smallpox killed countless millions – 300 million people in the 20th century alone – before it was finally declared eradicated on May 8 1980. It was a momentous day, marking what the current director general of the World Health Organization, Dr Tedros Adhanom Ghebreyesus, called the greatest “public health triumph in world history”.

As the weather cools, the number of infections of the COVID-19 pandemic are rising sharply. Hamstrung by pandemic fatigue, economic constraints and political discord, public health officials have struggled to control the surging pandemic. But now, a rush of interim analyses from pharmaceutical companies Moderna and Pfizer/BioNTech have spurred optimism that a novel type of vaccine made from messenger RNA, known as mRNA, can offer high levels of protection by preventing COVID-19 among people who are vaccinated.

Many countries are moving to exit a lockdown triggered by COVID-19, but the virus has not gone away and there are real concerns that a second wave of infection could happen. We urgently need to understand more about how the body deals with this infection and what we can do to tackle it. Immunology has taken centre stage here in revealing what happens when our body fights this virus, and brings us the possibility of treatments and vaccines.

A measles vaccine protects against measles infection. By introducing a bit of weakened virus, the immune system learns how to deal with it, so when a real measles virus comes along, it can eliminate it. But does the immune system learn more from the vaccine? Recent research suggests, rather intriguingly, that it does.