What is a breakthrough infection? 6 questions answered about catching COVID-19 after vaccination
Breakthrough infections are a little more frequent than previously expected and are probably increasing because of growing dominance of the delta variant. But infections in vaccinated people are still very rare and usually cause mild or no symptoms.
COVID: did a delayed second dose give the delta variant an evolutionary helping hand?
Viewed from the perspective of evolutionary selection, it seems that the UK government’s decision to lengthen the period between first and second vaccine doses provided delta with an extra window to infect people.