Dr. Meghani explains COVID-19 breakthrough infections, released on Halton's youtube channel. Halton Region's Medical Officer of Health answers five questions:
- What is a breakthrough infection? Does it mean the vaccine didn't work?
- How common are breakthrough infections?
- How severe are the symptoms of breakthrough infections?
- Can people with breakthrough infections transmit COVID-19 to others?
- Are COVID-19 vaccines really effective?
Transcription
Lately, I've been getting questions about breakthrough cases of COVID-19 and why people are still able to contract the virus, even when they are fully vaccinated. I've also heard anecdotal comments and questions about the value of getting vaccinated if breakthroughs are possible.
So, I want to take some time to walk you through what a breakthrough infection is. I also want to take a deeper dive into the data to help explain why getting fully vaccinated is so important and how it can protect you not only from contracting and transmitting the virus but also how it greatly reduces the risk.
So, let's get into it. Here are five things you need to know about breakthrough infections.
What is a breakthrough infection? Does it mean the vaccine didn't work?
A breakthrough infection is an infection in a fully vaccinated person who received their final dose of a COVID-19 vaccine at least 14 days ago.
While COVID-19 vaccines are effective at preventing infection, no vaccine is 100 per cent effective. COVID vaccines were not designed to prevent 100 per cent of infections. They were designed to prevent severe illness, hospitalization, and death, and they do that really well.
The vast majority of covid19 hospitalizations right now are in unvaccinated individuals, even though they make up only a small portion of the population.

Secretariat of the Science Advisory Table
The real-world evidence could not be clearer. Vaccines are working. Vaccinated people are significantly less likely to get sick with COVID-19 and less likely to end up in the hospital and ICU.
How common are breakthrough infections?
Breakthrough infections are rare in Canada. Most reported cases of hospitalizations and deaths are occurring among unvaccinated people. As an example, here in Halton, more than 440 000 residents are fully immunized, and less than 0.1 per cent of those people have been diagnosed with COVID-19 after full vaccination.
As of the second week of September, about 26 per cent of the Halton population remains unvaccinated. Many of these individuals are children under the age of 12 who are not yet eligible for vaccination. Like the data in the rest of Canada, here in Halton, the unvaccinated population made up almost two-thirds or 66 per cent of COVID-19 cases.
This is disproportionately higher.
How severe are the symptoms of breakthrough infections?
Breakthrough infections usually cause mild to moderate symptoms. Some fully vaccinated people may test positive for COVID-19 without experiencing any symptoms at all. Others may experience symptoms that would likely have been much worse had they not been vaccinated.
Most people recover quickly and stay infectious for a shorter period. A small percentage of breakthrough infections are in people with weakened immune systems, who are unable to respond as well to vaccines. Here too, symptoms are generally milder than if they had not received the vaccine.
In Ontario, some people with weakened immune systems are advised to get a third dose of vaccine to add an extra layer of protection.
Can people with breakthrough infections transmit COVID-19 to others?
The greatest risk of transmission is among unvaccinated people. Fully vaccinated people can still become infected and have the potential to spread the virus to others, although at much lower rates than unvaccinated people. However, vaccinated people are much less likely to become infected; therefore, they are less likely to spread COVID-19.
Recent studies also show that vaccinated people spread the virus for a shorter period. So, while it is much less likely for a vaccinated person to contract and transmit COVID-19, it is possible, which is why it is still important to wear a mask in indoor public places and follow public health guidelines.
Are COVID-19 vaccines really effective?
Regardless of your vaccination status, vaccines really do provide the best protection against COVID-19. This is what we know today. COVID-19 vaccines save lives. The vaccine is very effective in reducing your chances of getting infected. It also dramatically reduces your chances of going to the hospital. If you do become infected and it can save you from severe illness.
Even if you don't think you are at risk of severe outcomes because you are a young and healthy person, think twice. Young and healthy people are not immune to getting infected with COVID-19, ending up with long COVID symptoms. Getting vaccinated helps reduce the chance of infecting others, especially vulnerable populations such as those with weak immune systems.
The best way to reduce the number of COVID cases, including breakthrough cases, is to have as many people vaccinated as possible and ensure that we all continue to follow other preventative measures until we have a high level of community protection.
There are many options to get your COVID-19 vaccine. Learn more at halton.ca/covid-vaccines.
Let's do our part Halton, and please remember to continue to be kind to one another.
This post is a transcription from the video.