VANCOUVER -- More than 1.5 million people in B.C. have now received a COVID-19 vaccine, but the number of second doses distributed is much smaller.

With the government still targeting July 1 for offering everyone at least one shot, and a 16-week interval between immunizations, many will have only a single dose of protection for the summer.

As of Monday, 1,546,337 people in the province have gotten at least one shot, and 89,035 have received both doses.

UBC pharmaceutical sciences professor Dr. Fawziah Lalji said there is now real world data that shows even a first dose is effective at reducing serious illness and hospitalization.

She pointed to a study in Israel, where more than half of the population received a first dose of Pfizer. She said the study looked at a time period from December to February, and compared vaccinated people to unvaccinated people.

“They showed that the vaccine reduced symptomatic disease by about 57 per cent, and hospitalization by about 74 per cent,” Dr. Lalji said.

She added a public health study in England looked at the use of the Pfizer and AstraZeneca vaccines amongst elderly people, and found a first dose prevented COVID-related hospitalization by over 80 per cent.

“I think based on this data, individuals feel comfortable that you are well protected with the one dose of the vaccine,” she said. “Everyone does agree that we need two doses however, because what we don’t know is how long the duration of immunity will last with just the one dose.”

Dr. Lalji also said more needs to be learned about the efficacy of the vaccines on variants. She added when it comes to transmitting the virus, some studies show a single dose appears to be less effective on that front.

“The Israel study showed that it was around 46 per cent effective, and the U.K. studies have shown around that much as well,” she said. “So certainly not at the range of 80 to 90 per cent, which is what we’re talking about with hospitalizations.”

Lalji said there will be more studies looking at the effect on transmission.

“I suspect we will likely will need two doses for that to be really effective,” she said, and added most experts would suggest vaccination is just one additional layer of protection, along with measures like wearing masks and distancing, and other layers are needed until there’s greater herd immunity.

“Those layers will go very slowly, over time, making sure that we don’t get the flare-ups that we’ve seen in other countries and it’s uncontrolled transmission again,” she said. “I think for this summer...probably I suspect public health measures will still be very important and I think once we have a larger proportion of the population that’s double-vaccinated, then we will see a little bit more loosening of restrictions I think after that.”

Provincial health officer Dr. Bonnie Henry said taking measures to stop transmission is something “we all need to pay attention to” at this point in time, when cases are still high and not everyone has had a vaccine.

She added in other countries, when vaccinations have reached a certain level, transmission does start to decrease, and more pressure will be taken off the hospital system in B.C. as more people get vaccinated.

“We’re not there yet but there’s a lot of possibilities for what we can see later in the summer,” she said. “We need to be to be patient, and to stick with the program for the next few weeks, until we get enough people protected.”