Covid is Still Here (likely worse in fall), and Masks Still Work

Listen instead of reading (about 7 minutes)!

Jeff Gilchrist summarized the results of a recent study on mask mandates:

"Over only a six week period in 2022, during a period of sustained respiratory viral activity in Ottawa, Canada, kids being absent was reduced enough to gain almost 2,000 school days. This was with mostly low quality masks. Imagine how much better if everyone had proper N95s or better."

The study published last week by Nisha Thampi et al, compared three Ottawa boards that lifted mandatory masking policies in March 21, 2022 to the one board that reintroduced them on April 13, 2022 and found a "statistically significant decrease in student and staff absenteeism." There are lots of limitations to the study, but it's so clear that masks at least help reduce transmission, that it's bizarre we're not on board to keep them on in hospitals and schools. 

Mike Hoerger, PhD and founding director of Louisiana's HealthPsych PhD program, explains that the study underestimates the real and potential benefits of masking: 

"Real Benefits:
Often, schools that have stronger masking policies are lower socioeconomic status. They don't have high-level ventilation and HEPA filters, so masking becomes more important. Moreover, at the lower-SES schools, families are more likely to be multi-generational, have higher occupational exposure, and more in-home exposure (smaller homes, more people, less ventilation). Since it's not randomized which schools mask, the schools with good masking policies are up against many other obstacles. It's truly remarkable to see the pro-mask schools actually perform better against all of these other obstacles, so the real benefit of masking is likely underestimated. 

Potential Benefits:
Under universal masking policies, most children wear poor-fitting low-quality masks, such as low-filtration cloth masks or baggy blue procedure masks. There are also frequent mask breaks for snacks, lunch, and water. There has been very little emphasis on helping children wear masks that excellently fit their faces without gaps, and very little emphasis on high-quality masks like KN95s, KF94s, CAN99s, Flo Masks, and N95s (for teens). There's often very little serious consideration surrounding how to mitigate during meals and snacks. Distancing itself has very limited benefit in settings with low ventilation and filtration, which is often the case in schools. Well-designed masking programs would have a much more powerful benefit."

In another study just out, by Amy Peng et al., they used the fact that mask mandates were introduced and removed in an irregular fashion to evaluate the impact of community mask mandates. They found protective effects of masking to run from 15-42% depending on the choice of masks worn, which averted 290,000 clinical cases and 3,008 deaths. 

And this all runs in tandem with this prediction from epidemiologist and prof at U of T, Colin Furness, 

"What is going to happen with Covid this fall? Well, here's a worried thread: First, I do not believe we are seeing anything seasonal about Covid at all. Wastewater signals were elevated but not climbing all summer. Hot weather and being outdoors helped a bit, I'm sure. But it's important to understand why respiratory viruses are seasonal in the first place, and why Covid is different. 

Flu, colds (etc) have a basic reproduction number ("R0") only slightly higher than 1. Remember that R0 greater than 1 means sustained transmission; R0 less than 1 fizzles out. R close to 1 means these viruses need ideal conditions - lots of unmasked people sharing unfiltered, recirculated air - in order to propagate. We do much more of that in the winter than in the summer. 

But Covid has R0 greater than 12 (maybe even higher). It doesn't need ideal conditions.  That's why we had a significant rise in cases last summer - we removed any vestigial interventions, and the virus spread. So why didn't it happen this summer? In my opinion, it's more useful to ignore seasonality and look at what triggers waves: temporary immunity and new variants. 

All summer long, with static COVID rates, the temporary population immunity from high infection rates earlier in the year has been slowly waning. And evidently no new, hard-hitting, immune-escaping variant has emerged. XBB now dominates, but without a sudden wave. I say with confidence that no new, hard-hitting variant has emerged recently because much of the current Covid burden seems travel-related. Yes, that's right. Everybody flying everywhere with masking rates around 2% will ensure that any new variant that emerges anywhere will almost immediately be everywhere. (Yup: given what we know, nearly everybody traveling is choosing to act dangerously.) By this fall, we will start to create ideal conditions for viruses to spread (sharing unfiltered, recirculated indoor air). More importantly, it's at the same time that our temporary population immunity continues to evaporate. So cases will rise, and probably a great deal. Maybe it's already started, but it's also possible that the increase will really come in October, when we're indoors more. I don't know. If an efficient new variant also emerges, then we will have a very bad time. 

But I'm actually worried about another pattern: When kids go back to school in Sept, if Covid spreads rapidly, we may end up facing an immunity-theft problem leading to acute RSV like last year. The epidemiological pattern is now very clear to me: Covid just before RSV season is the perfect storm to be worried about. It's not just what that might look like, it's also the steadfast denial among infectious disease docs that this relationship exists. That ensures that we will do nothing to mitigate, or even to be ready. This won't necessarily be a disaster, I think much depends on when Covid levels rise in kids. If that happens later in the fall, even at the same time as RSV, that might not be so bad. It's when Covid comes first and THEN comes RSV that is the perfect storm, in my opinion. We saw this acute pattern in the US in Dec. 2021, but much less in Canada, because Covid hit there mid-fall, and hit us a bit later. But in fall 2022 we infected everybody, with concomitant immunity theft, just in time for RSV season: immunity recovers, it's about timing. I believe timing of "Covid --> immunity theft --> acute RSV" explains why I overestimated Canadian child risk in Jan 2022. In the US, Covid created an RSV crisis. But the wave hit Canada after RSV season. I sounded the alarm based on US data, without this insight. But if the medical community had listened to me in Jan 2022, they would have been prepared for the tragic wave of child RSV ICU admissions last fall. 

As it stands, we seem to be planning to be unprepared again. How bad it bites us will depend on Covid timing this fall."

I don't see mandates on the horizon, but if you have people you love in your life, consider wearing a mask to protect them and giving them the information they need to make an accurate risk assessment.