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Are you less likely to get COVID if you are vaccinated?

Some patients have seen reports about fully vaccinated people getting infected, and they are asking if this means the vaccines aren’t working. Others have asked if getting vaccinated helps prevent the transmission, or spread, of COVID-19. These are both important questions. 

What are breakthrough infections?

We have known all along that the COVID-19 vaccines are not perfect. Like other vaccines we’ve used routinely for years, they are highly effective, but not 100% (read more about vaccine effectiveness). 

When a fully vaccinated person gets infected, it is often called a “breakthrough infection.” There are a few things to know about breakthrough infections:

  • Doctors, scientists and regulators monitor for breakthrough infections very closely. In fact, Manitoba Public Health now reports new and active cases by vaccination status. 
  • The scientific evidence is confirming that the vaccines reduce the likelihood of getting infected with COVID-19, including against the Delta variant of concern.
  • The evidence is also confirming that when breakthrough infections happen, the chance is very low of getting seriously sick, requiring hospital care, dying or developing long COVID.

So, the vaccines help to reduce the chance of getting COVID-19 and they are still incredibly effective at preventing severe illness and death, including against variants of concern like the Delta variant. 

Do the vaccines prevent transmission of COVID-19?

The short answer is yes, vaccines reduce the chances of getting infected with COVID-19 and the likelihood that you will spread COVID-19 to others.

When we hear in the news that 15% to 30% of new COVID cases were fully vaccinated, it’s important to consider all the facts. This does not mean that 15% to 30% of fully vaccinated people are getting infected. 

Think of it this way. More than two thirds of Manitobans are fully vaccinated, but they are accounting for less than one third of new infections.

Because the number of fully vaccinated people is so much larger than the number of unvaccinated people, it’s important to think about it in terms of rates: What percentage of fully vaccinated and unvaccinated people get infected? 

An even better way to think about it is to compare the rates among fully vaccinated and unvaccinated people. A recent review by the Public Health Agency of Canada found that:

  • New cases of COVID-19 among unvaccinated people are 12 times higher than in the fully vaccinated people. 
  • Hospitalized cases of COVID-19 are 36 times higher among unvaccinated people than in fully vaccinated people. 

This visual helps to understand the relative risk of infections between fully vaccinated and unvaccinated people:

Health Canada reviewed cases of COVID-19 from December 14, 2020 when the vaccination program started through to August, 2021. While there were 10,176 cases of COVID-19 among fully vaccinated individuals, this accounted for only 1.5% of the 689,000 cases during this time period. 

Then why do vaccinated people still have to wear masks?
While the vaccines are very effective at preventing infections and spread, they are not 100%. At times when the risk of COVID is higher, it is important to follow public health recommendations to add additional layers of protection, such as wearing masks, to further reduce the risk of transmission. Because the Delta variant of concern is more transmissible than earlier COVID variants, these added layers of protection are important for the short term. 

Further Reading: