breakthrough infection

There are now some cases recorded of people acquiring COVID-19 even though they are fully vaccinated.  Such breakthrough infections, where the virus breaks through the protective shield of the vaccine, are rare but they cannot be discounted.  We should not in fact be surprised because we know that no vaccine has an efficacy rate of %100.  In this small group it is to be expected that there will be a large number who are completely asymptomatic, a small number who need hospitalisation, and a tiny number for whom the disease is fatal.

Breakthrough infections can occur among the elderly whose immune response to the vaccine is not as strong as it is for younger people.  And among the immune-compromised for obvious reasons. It can also occur in people who are being constantly exposed to the virus, as health workers.  And it seems that women are more likely to succumb to it than men, although no one knows why.