OTTAWA -- Experts say it's just a matter of time until Ontario has a new dominant strain of the COVID-19 virus.

The province’s deputy chief medical officer of health, Dr. Barbara Yaffe, cautioning that the Delta variant, first identified in India, is spreading rapidly in Ontario.

“Rapidly the U.K. [variant] is going down and the Delta is going up so we fully expect it will become the predominant strain,” Yaffe said.

In Ottawa, four confirmed cases of the Delta variant have been detected.

“[In] three to four weeks it will be crossing over the 50 per cent threshold of proportion of Delta in Ontario. So, it’s definitely coming in. It’s definitely going to be 100 per cent at some point,” Ottawa Hospital Senior Scientist Doug Manuel said.

Manuel says new consensus is that the reproduction rate (R) of the Delta variant is now positive, meaning for everyone the virus transmits at a one to one rate.

“The best guess, a bit speculative, but we’ll be in positive growth for R for Delta, cases will start to increase and then [the question is] can we vaccinate our way out of it,” Manuel said.

According to Dr. Yaffe, the Delta variant spreads one and half times faster than Alpha variant and new studies from Scotland estimate the Delta variant doubles the risk of hospitalization compared to the Alpha strain.

“People that are on one dose of the vaccine seem to be more susceptible to becoming a case with the Delta variant than with the Alpha, which is quite concerning,” Aris Katzourakis, a professor of evolution and genomics at the University of Oxford said.

Katzourakis notes the surge of Delta variant driven cases in the United Kingdom has lead to an increase in hospitalization.

“It’s not clear exactly what proportion of infections may lead to hospitalization depending on different vaccination statuses but that’s a very concerning area that we’re keeping a very close eye on,” he added.

Data released this week from Public Health England suggests that after a single dose, the AstraZeneca vaccine is 71 per cent effective against hospitalization and Pfizer vaccine is 96 per cent effective.

“It really, really underlines the importance of rolling out that second dose to people, especially to locations which have raging Delta variant pandemics,” Katzourakis said.

In Ottawa, those with two doses of the vaccine say they’re more thankful than ever.

“It’s a huge relief for myself, the family and especially dad,” John Cau, whose 98-year-old father Nick got his second dose on Tuesday, said.

“I can’t wait to get mine,” Cau added.

Even those with a single dose of the vaccine say they feel safer knowing they have some level of protection against the new variant.

“Very, very safe; way better than before,” Simon Hughes said.

“Yeah I feel more comfortable, for sure,” Ana Perez added.

Manuel says keeping cases low will be key to manage the spread of the variant, something Ottawa Public Health could do though intensive contact tracing of any new clusters.

“We need to transition our whole pandemic [strategy] to more of a cluster buster. We just treat it as Delta and then we really go after not only the person and their contacts but where they got it from,” he said.