When people get covid but don’t have symptoms, they

• spread the virus,
• don’t develop much immunity to future infection,
• and can get long covid.

Most countries have done very limited asymptomatic testing and most research is obviously on symptomatic people, so it’s hard to know how many people this group includes.

This meta-analysis summarizes what we do know and it’s not great.

The pooled percentage of asymptomatic infections was 0.25% among the tested population and 40.50% among the confirmed population. The high percentage of asymptomatic infections highlights the potential transmission risk of asymptomatic infections in communities.

0.25% is high, but remember that testing isn’t random – travellers, pregnant women, healthcare workers feature heavily in the sample.