All adults in Ontario are now eligible to get their second booster—or fourth shot—of a COVID-19 vaccine.

The new eligibility, which was announced on July 13, was met with mixed reaction. This was in part because the province’s chief medical officer of health said that while all adults will be able to get the shot, he isn’t recommending it for everyone.

Here’s what you need to know:

Who can get the fourth dose of COVID-19 right now?

All adults aged 18 and up, who had their third dose at least five months ago, can get the shot.

According to the Ministry of Health, people who get infected with COVID-19 after a complete primary series should wait three months to get their booster dose; however officials recommend discussing timing with a health-care provider.

“People may also receive a COVID-19 vaccine as soon as they are asymptomatic,” the ministry said. “However, longer intervals between infection and vaccination may result in a better immune response.”

Why wouldn’t I get the fourth dose?

Dr. Kieran Moore told reporters that while all adults are now eligible, those that are healthy may want to wait until the fall to get the new “bivalent” vaccine that targets the Omicron variant.

“While we're making this option available, it is important to note that healthy, currently vaccinated individuals, continue to have significant, persistent protection against severe disease even six months after the last dose,” he said at the time.

“However, there may be individuals with personal or medical circumstances in those age groups who may benefit from an additional protection of a second booster.”

So, should I get a fourth dose?

Moore said that individuals who are immunocompromised or who may benefit from additional protection should get the booster. Personal circumstances—such as individuals who work in congregate settings or live with at-risk family members—may also choose to get it.

Officials are encouraging residents to speak with their health-care provider about whether or not they should get the dose.

This follows recommendations made by the National Advisory Committee on Immunization, who says it is most important for older adults and those at risk of severe COVID-19 infection to get the boosters.

If I get a second booster, will I still be able to get the new one in the fall?

Yes. Officials have said that while timing and eligibility information has yet to be finalized, individuals who received four doses of COVID-19 will be able to get a fifth after the soon-to-be-specified interval time. This may mean you have to wait a month or two longer than those who hold off on getting their shot.

What’s the difference between this vaccine and the new one?

The new bivalent vaccine is expected to target the Omicron variant specifically. The first vaccine offered to Canadians was developed to offer protection against the original novel coronavirus strain. It is still effective in reducing risk of hospitalization and death among newer variants; however the newer vaccine will, similarly to the flu vaccine, target the latest version of the virus. In this case, the bivalent vaccine will target both the original strain and the Omicron mutation.

When will the new vaccine be available?

The bivalent vaccine is expected in the fall. Moore suggested that depending on whether manufacturers want to target the BA.5 subvariant specifically it could be distributed in November or December.

Who will get the new vaccine first?

Those details are still in the works, but the Ministry of Health says they expect to “prioritize more vulnerable populations by age and risk, as needed depending on vaccine supply.” In the past, Ontario has started distributing vaccines to long-term care homes, as well as people over the age of 60, individuals who are immunocompromised, or adult First Nations.

How do I book an appointment?

Individuals interested in getting the fourth dose can book an appointment using the same platforms available for the third shot—either through the provincial booking system or their local public health unit.

Do I need a booster shot at all?

Health officials and experts all say that a third dose of COVID-19 vaccine is recommended for all adults over the age of 18, as well as youth between the ages of 12 and 17 who are immunocompromised.