OTTAWA -- Ottawa surpassed 20,000 total COVID-19 cases since the start of the pandemic on Monday, but there is a significant difference between the outcomes of the first 10,000 cases and the second 10,000 cases.

Data from Ottawa Public Health show that the raw fatality rate from COVID-19 has dropped significantly in the past three and a half months.

From March 11 to Dec. 31, 2020, Ottawa Public Health recorded 10,051 cases of COVID-19 in the city and 392 deaths from the disease, for a raw fatality rate of 3.9 per cent.

From Jan. 1 to April 11, 2021, OPH reported 10,022 cases of COVID-19 and 84 deaths, for a raw fatality rate of 0.84 per cent.

Case counts have been rising significantly in 2021. There have been two major spikes, one in January and one that is ongoing now, but these cases have not led to a similar number of deaths.

Local public health officials are not yet able to say definitively why the number of deaths related to COVID-19 is lower now compared to last year. There are several variables at play, including but not limited to co-morbidities in COVID-19 patients, vaccine coverage, better response measures taken to protect the most vulnerable, and now the variant strains in the community.

Epidemiologists refer to a phenomenon known as "mortality displacement", in which reports of deaths in the population during events such as pandemics occur in greater numbers earlier on and decrease in subsequent weeks. This can be observed in Ottawa where 244 of the 392 reported COVID-19 deaths in 2020 were reported between March 25 and May 31.

Data from the Ontario government show a stabilization of the rate of deaths per 100,000 residents since early 2021. The weekly trends show a spike of 1.2 deaths per 100,000 residents reported the week of Jan. 17 to 23. Since that time, the weekly rate has not climbed above 0.8 per 100,000.

For comparison, the rate hit an all-time high of 5.8 deaths per 100,000 residents during the week of April 26 to May 2, 2020.

According to OPH, the recorded number of COVID-19 deaths includes Ottawa residents with laboratory-confirmed COVID-19 who died. Deaths are included whether or not COVID-19 was determined to be a contributing or underlying cause of death.

There is some data to suggest a correlation between increased vaccination coverage in Ottawa and the lower fatality rate.

In 2020, roughly 85 per cent of all COVID-19 related deaths came from outbreaks, largely in long-term care homes and retirement homes.

However, residents of those homes are now fully vaccinated. OPH data show that 91 per cent of long-term care home residents had received both doses of COVID-19 vaccine as of Feb. 11, 2021 and 89 per cent of retirement home residents had both doses as of March 20.

Since Feb. 11, there have been two deaths linked to outbreaks in long-term care homes.

Additionally, OPH data show that, as of Monday, more than 85 per cent of all residents 80 to 89 in the city and more than 87 per cent of residents 90 or older have had at least one dose of a COVID-19 vaccine. Those two age groups account for 71 per cent of all reported COVID-19 deaths in Ottawa to date.

The COVID-19 pandemic remains ongoing with a surging third wave and hospitalization rates even higher than during the first wave in 2020. Experts continue to urge residents to follow all public health protocols, including physical distancing, limiting close contacts, mask use, handwashing, self-isolating when sick and seeking COVID-19 testing when showing symptoms.

Ottawa remains under an Ontario-wide stay-at-home order.