Do I need a fourth dose? Ontario experts answer questions about second COVID booster

The choice to get a fourth COVID shot has been left in the hands of the young and healthy.

It is up to the individual," said Dr. Zain Chagla, infectious disease physician at St. Joseph's Healthcare.

Unlike other doses, there is no universal recommendation for those under age 60 with no underlying health conditions.

It's not black and white," said Dr. Fahad Razak, scientific director of the Ontario COVID-19 Science Advisory Table.

The decision can be a tough one so Razak and Chagla provide some answers to help make an informed choice.

Who should get a fourth dose?

There is no question that adults age 60 and over should get a fourth shot now. It's also recommended for Ontarians who are moderately to severely immunocompromised.

These folks have been eligible for some time, there is prevention from severe disease and death in this age group, and so people should head out to get their shots," said Chagla.

Razak agreed saying, High risk groups, go get it now."

Who should consider it?

Razak suggests three groups of young and healthy adults might consider getting a fourth dose now:

• Those who had their third shot six months ago or longer;

• Front-line workers worried about a higher chance of potential exposure; and

• Close contacts of those at higher-risk of severe infection.

Shouldn't everyone get a fourth dose?

It might be better for some individuals to wait, especially as the data for fourth doses is temporary protection in younger individuals," said Chagla. On top of this a lot of people with three doses got Omicron, and so they are functionally boosted in that context, so may be worth it to wait."

Why wait?

There is a novel vaccine likely coming in the fall, plus the fall respiratory season, and we know longer intervals can lead to better responses," said Chagla.

The new shot is bivalent, which means it targets the original coronavirus strain as well as Omicron.

The Moderna vaccine data suggests higher antibody responses to Omicron with the bivalent vaccine," said Chagla That's good news going into a high transmission season."

But Razak cautions the difference might not be as dramatic as hoped with the new vaccine - plus, the virus is constantly evolving so it's hard to say what the fall will bring.

What does the fourth shot do?

It will temporarily give protection against infection but this is very short lived," said Chagla.

He said it's likely to last six to eight weeks compared to more than 20 weeks with the third dose.

In a young healthy person those benefits are tiny," said Chagla.

However, it's worth it for those who are older and immune compromised because it will reduce their risk of severe disease," he said.

Is the pandemic almost over?

Ontario - including Hamilton - is in the midst of a seventh COVID wave. Hamilton public health has reported COVID transmission is currently high and increasing. Scarsin Forecasting has predicted spread to greatly increase" in the fall in Hamilton.

The bottom line

For young and healthy Ontarians, the third dose is the most important.

The biggest opportunity that hasn't been pursued is the third dose," said Razak. There's very clear evidence it's highly effective."

Chagla agreed saying, Three shots still offers significant protection from severe disease."

Joanna Frketich is a health reporter at The Spectator. jfrketich@thespec.com