Why are fully vaccinated people still catching Covid-19?

As the number of fully vaccinated people continues to grow in SA, questions about why some people are still becoming infected with Covid-19 are thrust into the spotlight.

According to government stats, more than 12-million people have been fully vaccinated, with over 5-million Johnson & Johnson vaccines administered, just under 7-million second Pfizer vaccines given and just under 100,000 single-jab shots administered to 12-17-year-olds.

The US Centers for Disease Control and Prevention (CDC) states that Covid-19 vaccines are effective at preventing infection, serious illness, and death. However, they are not 100% effective at preventing infection and some people who are fully vaccinated can still get the virus.

An infection of a fully vaccinated person is referred to as a “vaccine breakthrough infection”, said the CDC.

“Fully vaccinated people with a vaccine breakthrough infection are eight times less likely to develop serious illness than those who are unvaccinated and get Covid-19.

“Even when fully vaccinated people develop symptoms, they tend to be less severe than in unvaccinated people. This means they are 25 times less likely to be hospitalised or die than people who are not vaccinated. People who get vaccine breakthrough infections can be contagious,” said the CDC. 

The World Health Organisation's Dr Kate O’ Brien explained that there is little data from clinical trials on whether vaccines protect people from getting reinfected. 

“The clinical trials demonstrated that these vaccines protect people against disease. What we don't know yet from the clinical trials is whether the vaccines also protect people from just getting infected with the virus and whether it protects against transmitting to somebody else,” O’ Brien said.

“So, this is a really important part of our understanding about what these vaccines do. Do they only protect against disease or do they also protect against getting infected and being able to transmit to somebody else, even if you're not having any symptoms,” she added.