The cruel math of the pandemic

But you don’t get to quit the marathon: get boosted, stay home when sick, and wear a mask

“This is where the maths of endemic infectious disease is quite cruel in the face of attempts to reduce the average prevalence of a highly infectious pathogen: some of the benefit of the intervention gets sucked up in compensating for the reduced level of immunity.”

– Professor Michael Plank

The value of wearing a mask is not what it used to be. Wearing a mask may diminish the impact of spread that is facilitated by waning population immunity, but the outbreak may still occur, just smaller. And for formerly COVID-zero jurisdictions, such as Newfoundland and Labrador, that is not the value for money we are used to seeing. Until December 2021, our public health measures got the job done and eliminated COVID. Again and again. But then two weeks later, Chief Medical Officer of Health, Dr. Janice Fitzgerald, stated ‘most people will get COVID’. At the time (Jan 4, 2022), Newfoundland and Labrador had reported 20 COVID-19 deaths in a population of 522,875. In two quick weeks… what exactly? You’re telling us the magic has gone? Most people will get COVID: that is the cruel math of a highly infectious pathogen, circulating globally, and evolving increased infectiousness in response to our efforts to develop vaccines and prevent spread.

The Michael Plank quote is from a New Zealand media article written by Keith Lynch titled “COVID NZ: why long-term Covid restrictions are less effective than advertised”.

The article makes the following points:

• Permanent immunity from COVID-19 is not possible because our immunity wanes;
• Delta outbreaks were mostly controlled in New Zealand by vaccination. (The same is true of Newfoundland and Labrador, although, I would add, the strong public health response including test-trace-isolate and community compliance was also critical);
• Due to its high infectiousness even in vaccinated and previously infected populations, no country, other than potentially China, has controlled outbreaks of the Omicron variant;
• Some arguments for the implementation of control measures assume the measures will bring the reproduction number, \(R_t\), below 1 and eventually eliminate the outbreak. For the Omicron variant, the evidence is not there to support this assumption. More likely is that measures would reduce, but not bring the outbreak under control, and not lead to eventual elimination of the outbreak (this insight is due to Adam Kucharski, Co-director of the London School of Hygiene and Tropical Medicine);
• Mitigation measures, such as mask wearing, will still reduce spread: fewer people will be hospitalized and peak hospitalizations will be less, protecting health care capacity;
• Effective measures also leave more people susceptible. Measures can have surprisingly weak effects as the future potential for infections remains. (Insight due to COVID modeller James Ward.)

It is not feasible to eliminate the Omicron variant in formerly COVID-zero New Zealand. It is not feasible in formerly COVID-zero Newfoundland and Labrador either. But with the gold medal out of reach, we are not packing up and failing to finish the marathon. As stated on Keith Lynch’s twitter his article describes: ‘An uncomfortable #COVID19 reality we need to face up to’. This is an honest article. It sets expectations for what can reasonably be achieved, so that we can credit a strong response, when a strong response has occurred, instead of discrediting our work and achievements because we have failed to reach an always-impossible standard.

In the United Kingdom, Independent Sage released a 7-point plan for future COVID management: 1. Clear messaging; 2. Increased vaccine uptake; 3. Improved ventilation; 4. Access to rapid tests; 5. Financial support for workers during self-isolation; 6. Promotion of wearing high-quality masks; and 7. Support for global provisioning of vaccines and antivirals. This plan is available as a video here.

And lastly, as far as the New Zealand-Newfoundland and Labrador comparisons go, consider this brilliant cartoon:

Mask up pic.twitter.com/iZwuDLoDk5

— Eileen Kiffin (@KiffinEileen) July 25, 2022

Janice is incorrectly spelled as “Ash”, they mistakenly think she is leaving, and that kea should be a puffin, but you get the point: it was you all along.

Regarding situational awareness for Newfoundland and Labrador, my advice is as follows:

1. The best situational awareness are the statements by Dr. Fitzgerald. On July 13, 2022, Dr. Fitzgerald stated we should expect to see cases and hospitalizations rise over the next 2-3 weeks due to the BA.5 subvariant.

2. The number of people in hospital is reported every Wednesday at noon. Consider about 9 days from exposure to hospitalization. The number of people in hospital is a very approximate guide for the relative infection risk 9 days earlier. The reported number of people in hospital was: 13, 8, 14, and 16 over the last 4 weeks. For context of how this compares to the BA.1/BA.2 wave, see here.

3. Consider wastewater. The virus levels in wastewater are a guide for infection prevalence in that catchment. As these represent catchment-level patterns, implied infection prevalence can reasonably be transient due to it being only a local representation. There is some sensitivity to rainfall and methodology.

4. Test positivity and between province comparisons may not be good indicators of situational awareness. On March 15, 2022, Newfoundland and Labrador stated that number of tests completed would no longer be reported as it is not an accurate representation of the testing occurring (this number is the denomenator of a test positivity calculation). Test positivity for a random population sample (for example, hospital admissions might be considered as such) is a better indicator of infection prevalence in the community. Inconsistencies in how testing occurs between jurisdictions can lead to fraught comparisons. To the best of my knowledge, anyone with symptoms remains eligible for testing in Prince Edward Island, the results of which would be included in the provincial case counts, while in all other provinces most of the population are recommended to complete rapid tests, the results of which are not captured in the provincial case counts.
   

In conclusion, unless you have been recently infected, infection risk due to BA.5 is currently quite high in Newfoundland and Labrador. You should get boosted if eligible, you should wear a mask, and you should self-isolate for the required 7 days if you test positive.