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How much immunity does a previous COVID-19 infection offer? B.C.'s top doctor weighs in.

Dr. Bonnie Henry explains what protection you get from a previous COVID-19 infection.
Bonnie Henry January 22
Dr. Bonnie Henry said on Feb. 9, 2022, that a previous COVID-19 infection does not develop both parts of the immune system in an unvaccinated person. 

A COVID-19 booster dose increases immunity by over 50 per cent but a previous infection in an unvaccinated individual does not warrant the same type of protection, says B.C.'s top health officer. 

While a previous coronavirus infection offers some immunity against reinfection, provincial health officer Dr. Bonnie Henry told reporters in a press briefing on Wednesday (Feb. 9) that it does not develop both parts of the immune system in an unvaccinated individual. 

"So, what we call the humoral immunity — the antibodies in your blood — and the longer-lasting, stronger protection you get from cell-mediated immunity," she explained. 

Henry added that health officials are seeing more cases of unvaccinated people who test positive for Omicron and do not develop both parts of their immune system. Additionally, it is less clear how much protection a previous infection offers and for how long it lasts. 

People who have had a previous infection — whether they have been vaccinated or not — need to build up their immune system for the "long-term" by getting immunized, Henry stressed. This may mean receiving a full course of a Health Canada-approved vaccine or getting a booster dose. 

Individuals who were recently infected with COVID-19 may wait as long as eight weeks until they start their immunization but there will be some degree of risk in that period of time, the health officer said. 

"What I've been saying all along is that it is important that once you have recovered from infection and are no longer infectious to others, that you can receive your vaccine anytime after that," she said.

"If you are somebody who's immune-compromised or has receptors for severe illness, that is when you should get your vaccine. This applies to booster doses, too."

Individuals who do not have any underlying conditions that put them at risk may wait as long as three months after a COVID-19 infection, noted Henry, adding that "all of this is slightly confusing." 

The health officer underscored that the booster dose will offer about 50 to 60 per cent protection from Omicron, however. With the amount of transmission in the community, she added that people should get their third dose within six months of their second regardless of whether they've had an infection in the last few weeks. 

"As we get to a place where there's less virus circulating, that advice may change and it may be prudent or maybe OK to wait a little bit longer," she told reporters.

"But I encourage everybody when there's a lot of virus around, vaccination helps."