BA.2 variant, waning immunity to push ‘resurgence’ of Hamilton COVID-19 infections: public health

Hamilton public health (HPHS) is predicting a resurgence of COVID-19 cases and hospitalizations through the spring of 2022 due to increased transmission of BA.2 variant and relaxed public health measures.

During a board of health meeting on Monday, the latest Scarsin forecasting is suggesting COVID-19 will continue to circulate in the city well into June and that residents will be more susceptible to infection with immunity waning.

Current epidemiological data suggests the city is now on course with a so-called “resurgence scenario” — the worst of two forecasts presented to city councillors in March — that could produce 400 new COVID hospitalizations between now and the end of June.

“New hospital admissions are likely to continue into the summer and may reach almost six per day,” Hamilton public heath epidemiologist Ruth Sanderson told councillors.

The updated numbers suggest the impact of Omicron subvariant BA.2 represents around 45 per cent of all cases now sprouting up in Hamilton as of the end of March.

It’s expected that overall COVID case numbers in the next few months will be half of the peak seen during the Omicron wave in mid-January with the latest wave expected to hit a high in early May of about 650 cases per week.

Peak hospitalizations are also expected to be half of the 14 admitted per week in mid-January.

Those aged between 60 and 79 are the demographic most likely to be impacted by potential hospitalization during the next wave.

It’s estimated 16 COVID-related deaths are possible between now and the end of June.

Hamilton’s medical officer of health Dr. Elizabeth Richardson used the BOH meeting to urge residents to continue exercising protective measures and keep up to date with COVID booster shots, reducing potential serious outcomes with the increasing infections.

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“While we are not in a mandate situation, we are very much encouraging people to use those measures in order to reduce the risk of transmission to themselves and to their loved ones,” Richardson said.

The top doc says the city is working with the province on campaigns encouraging booster doses, to avoid further public health restrictions, saying it’s “the most important piece” in reducing the severity of cases likely ahead.

“We’re continuing to work on that path, but there would be a change if we saw some significant changes in those other indicators,” said Richardson.

Hamilton has been seeing an increase in daily COVID-related hospitalizations moving from a seven-day average of about two cases per day to around three as of April 1.

The lagging indicator is up as data tied to daily case numbers and the detection of coronavirus in wastewater have risen since mid-March.

Epidemiologist Erin Rodenburg told councillors that while reported overall case numbers continue to be “underestimated” due to a lack of PCR tests, there is an increase in that metric which coincides with a growth in infections among the population.

“When we see both increasing, we have good confidence that is really reflecting increased transmission in our community,” Rodenburg said.

As of April 4, the city’s per cent positivity rate was at 19.2 per cent based on just under 4,000 recent tests.

Ontario reported 857 people in hospital with COVID-19 on Monday. There are 168 people in intensive care (ICU) with or due to the virus — an increase of 94 hospitalizations and two people in intensive care since Sunday’s report.

Hamilton’s ICU admissions continue to be near zero as of the end of last week.

In the last two weeks, Rodenburg says institutional outbreaks have been on the rise as well, moving from the five to 10 reported per day a month ago to about 15 at any given time in late March.

As of Monday, Hamilton has 13 confirmed institutional outbreaks tied to 109 total cases.

Six of the surges are connected to seniors homes with three at long-term care homes (LTCH). More than 50 of the city’s current outbreak cases are with the St. Joseph’s Villa LTCH.

Three hospitals, four support homes and the Hamilton Wentworth Detention Centre account for the remainder of the ongoing outbreaks.

There are four suspected surges at a pair of shelters and at two homes with seniors.

Rodenburg says Hamilton’s wastewater data indicators are also now showing “consistent increases” in unison with all other indicators public health is relying on to measure the effect of the latest COVID wave.

The epidemiologist says the signal, normalized against a marker accounting for environmental changes in the sewer shed, has seen consistent increases in coronavirus content since mid-March.

“So when we see those consistent increases in all of these indicators, we can confirm that we are seeing increased COVID transmission in our community currently,” Rodenburg said.

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Prof. Robert Delatolla with the department of civil engineering at the University of Ottawa, who manages Hamilton’s wastewater data, says the science involves the SARS-CoV-2 virus’ appearance in the gastrointestinal tract of an infected individual and its eventual expulsion through human feces.

Surveillance involves collecting samples from the Woodward Avenue Treatment plant, isolating trace levels of coronavirus particles, and exposing them through PCR testing.

“So we do a number of steps where you can isolate that component, where it would be, and then … measure a biomarker to how much fecal matter is in that component,” Delatolla told Global News.

“We use those two measurements to get a concentration that’s essentially … the virus within the community.”

Hamilton’s medical officer of health on numerous occasions had said wastewater data “doesn’t correlate” with other COVID data sources the city’s public health unit has been using.

Dr. Bart Harvey, who manages the metric for the city, says the measure has improved usefulness but still presents “lagging” information in the same vein as data from cases and hospitalizations.

“To date, HPHS has found case numbers, per cent positivity, and COVID-19 hospitalization data to be adequately representative of COVID-19’s current prevalence in Hamilton,” Harvey told Global News in mid-March.

“We continue to work with the province and the researchers at the University of Ottawa to understand how this study is being incorporated into monitoring metrics going forward.”

Hamilton’s COVID-19 vaccination program has reached over 90 per cent of Hamiltonians aged 12 and up in first dose coverage. About 88 per cent have had second doses while 53.5 per cent have had at least one booster.

Richardson characterized the city’s program as “fairly stuck” with little change in numbers since the last board of health meeting in early March.

The city’s average shots per day (404) through March were off by 57 per cent compared to February’s 945 every 24 hours and distant compared to January’s average of about 4,500 shots per day.

The city lags behind Ontario, which is reporting 93 per cent of those aged 12 and older with at least a single dose and 91 percent fully vaccinated.

As of April 3, the city has put about 1.22 million COVID-19 vaccine doses into arms with about 470,000 second doses and 290,000 third shots.