Using access to information legislation, the CBC obtained COVID-19 modeling updates prepared by the Department of Health and Wellbeing’s analytics division.
The updates show the province’s projections of how many people will need acute care hospitalizations and ICU admissions between January and the end of May. The models were updated at least 13 times during this period as new information became available.
Tara Moriarty, an infectious disease researcher and associate professor at the University of Toronto’s school of dentistry and medicine, said all models during the pandemic need to be updated frequently. “The situation is constantly changing, and we have to keep changing,” he said.
Tara Moriarty is an infectious disease specialist and researcher at the University of Toronto. (Lisa Xing/CBC)
Moriarty is part of a group of scientists called COVID-19 Resources Canada. The group hosts a weekly online discussion sponsored by the Public Health Service of Canada, where scientists volunteer to answer questions about COVID-19 for the public.
“The models are usually pretty good for the next month and beyond, if there are uncertainties about new things that might happen, that can change those models,” he said.
A major change to the Nova Scotia models occurred between the issue dated February 23rd and the next issue dated March 28th.
(CBC News)
The February model showed the number of acute care patients falling steadily in March, April and May.
However, on March 28, the analysis team released a new version showing that the number of patients in acute care rose again in April to more than 50 patients and leveled off in May and June.
This was after the reopening measures started with the first phase on 14 February and progressed to a full reopening in the third phase by 21 March.
The modeling team analyzed the virus’s reproduction number, a measure of how quickly infections spread. A reproduction number greater than one indicates that cases are increasing and less than one indicates that they are decreasing.
The presentation said that the playback number started to rise “shortly after the restart phase 1 (February 14), reached around the level of 1.8-2.0 by March 15 (Phase 2) and remained at this level for 10 days (Phase 3).”
The March 28 model accurately predicted the number of people in acute care during what the modeling team called the “post-reopen wave” would not exceed 90 patients at a time, which is how many people were admitted during the peak of the Omicron wave.
The model also predicted an “extended plateau of hospitalization.”
At a media briefing Monday, Dr. Robert Strang, Nova Scotia’s chief medical officer of health, defended the province’s options for reopening.
“Over two years we’ve learned lots and lots about the virus,” he said. “We learned a lot more about how it was transmitted, and a lot of the measures we initially put in place weren’t really necessary to limit transmission.”
Strang also noted that vaccines are powerfully protective against serious diseases.
Dr. Robert Strang gives an update on COVID-19 on February 9, 2022. (Communications Nova Scotia)
“Our Public Health response has always been to minimize overall harm, not just minimize the harm from COVID. All of these tight restrictions have had significant impacts, whether it’s economic or mental health. Now we’re seeing significant impacts on health from delayed access to care due to some of the restrictions that have been put in place in our health care facilities. We continue to work to find a balance that limits overall harm.”
The modeling team noted that during the Omicron wave the province did not have an accurate count of the number of people getting sick, so it was not possible for the models to predict daily case numbers. Because of this, the modeling team focused on predicting hospitalizations and ICU admissions.
None of the models attempted to predict the number of deaths.
what is happening now
As of Wednesday, Nova Scotia has lifted all community-related COVID restrictions, although some restrictions remain in high-risk places, such as long-term care homes. “I don’t expect the lifting of restrictions to have a significant impact on its own,” Strang said in response to a question about how the move would affect the health care system. “We have to look at the bigger picture, not just the health system.” Models from late May give a look at possible future scenarios where acute care and ICU patients decline in numbers through July and early August. The model at the end of May said the reproduction number fell below one in April and continued to decline through May. He predicts that by August there will be an average of five patients in urgent care and three in ICU. “We will still see some cases in the community (travel-related, accidental/sporadic or local outbreaks),” the presentation warned. Jack Woodhead becomes the first child in Nova Scotia to receive the COVID-19 vaccine at the IWK Health Center on December 1, 2021. (CBC) In an email this week, the Department of Health confirmed that hospitalization modeling was last updated on June 28 and that modeling was consistent with previous forecasts.
Isolate when you are sick
Tara Moriarty, an infectious disease expert and researcher at the University of Toronto, said she is concerned about the spread of the BA.5 Omicron sub-variant and believes it was “not a good time” this week to lift the mandatory self-isolation requirement in Nova Scotia.
However, he said what happens next will depend on how the public behaves. “Making it mandatory might not have had much of an effect on people’s behavior,” Moriarty said.
“Many people may be isolating themselves, and whether it’s mandatory or not, [Public Health] don’t think it will work. But in general you definitely want to send a message to people that you should isolate yourself when you’re sick.”
In this file photo, a person undergoes a COVID-19 test. (Steve Lawrence/CBC)
The predictions released to the CBC were created before this week’s changes were announced. The province says those models did not take into account Monday’s announcement, but assumed “minimal public health restrictions and good public information and compliance.”
They do not show how waning immunity from vaccinations will affect hospitalizations, which the modeling team said should be taken into account in the future.
Strang said this is an area the National Advisory Committee on Immunization (NACI) is studying, and his department is incorporating its guidance. “Last week some fall booster recommendations came out that we’re starting to look at now,” he said.
A scenario created in early May shows the modeling team considered an early summer outbreak between June 15 and July 30 that would see some community spread out for about four weeks.
“This outbreak has minimal impact on acute care admissions,” the model presentation said.
Strang said his department is aware of the possibility of a resurgence of newer Omicron sub-variants later in the summer, but no specific plan has been developed for that possibility.
“We know all the measures we’ve used for the last two and a half years,” he said, noting that the department will assess the severity of any outbreak. “We’ll go back to the tools we used before.”
MORE TOP STORIES
