Covid-19: An Unsympathetic Predator
Just when we thought we had Covid cornered, it seems to have executed a delicate Cabriolé and is now poised to begin the dance anew.
Covid cases have been rising dramatically in many parts of the world, including Canada. In Ontario, in the last half of July, the incidence of new daily cases fell as low as 119, and the 7-day moving average to 157. As of August 31, however, new cases per day stood at 656 and the 7-day moving average at 701. The increase in cases puts Ontario into a position roughly similar to that in June of this year, and substantially higher than one year ago.
The culprit? At last in part, the Delta variant. Delta exhibits far higher viral loads than other strains and is on the order of twice as transmissible. It is responsible for new outbreaks in India, the UK, South Africa, the United States, Asia, and elsewhere. While Delta currently constitutes only about 3.6% of all Covid cases in Ontario, Toronto is the country’s leading Delta “hot spot”, and it seems likely that it will not be long before we are jumping on the Delta bandwagon.
There are studies suggesting that the popular vaccines are nearly as efficacious against Delta as for other strains (although as noted below, this is disputed by some scientists). However, efficacy declines over time. Israel, for example, was one of the first out of the gate with vaccinations. However, with declining efficacy, Israel is now experiencing an aggressive third wave, and many of the fatalities are in respect of those who were double-vaccinated. The Israeli Health Ministry reports that by August, the efficacy of the Pfizer vaccine fell to 39%, and an astonishing 16% for those double-vaccinated before the end of January 2021. A large-sample UK study reports comparable drops in vaccine efficacy.
Just as alarmingly, it is now recognized that those who initially suffer no or mild symptoms can nonetheless go on to experience “long-Covid” – the delayed appearance of a litany of debilitating symptoms that includes serious cognitive and motor impairment, and possibly even permanent damage to vital organs. Long-Covid is not the exclusive province of the aged or infirm. One study found that long-Covid afflicted 52% of the authors’ sample of 16-30 year-olds, none of whom were initially hospitalized. Another found that 14.3% of patients with initially mild or asymptomatic cases experienced long-Covid.
The heightened risk to older people is often under-appreciated. One study found that persons aged 60-69 are nearly 19 times more likely to die from Covid than younger persons. Those aged 70-79 are 44 times more likely to die, and the figure rises to 87 for those ≤ 80 years. The heightened risk to older folk is about the same as a comorbidity factor such as serious heart or respiratory disease. As a result, the American CDC has stated that wherever possible, all those 65 and over should be given the option of working remotely.
Whether airborne Covid is transmitted only via “droplets” or also by “aerosols” is hotly debated. Droplets are classified as globules that are > 5 microns in size, while aerosols are ≤ 5 microns. The conventional thinking is that droplets settle to the ground within 3-6 feet of their source. By contrast, aerosols rapidly evaporate, creating a field of ultra-small particles that may remain suspended in the air for hours and travel significantly farther than 6 feet. While mask-wearing and maintaining 6-foot separation work effectively as safeguards for droplet transmission (at least in a well ventilated space), aerosols can penetrate masks, rendering these protections insufficient.
Many scientists believe that droplets are the only transmission vector for Covid, but others disagree. In particular, studies emanating from a group of scholars at M.I.T. empirically demonstrate that sneezes and coughs can generate a “turbulent puff cloud” in which droplets are expelled at high velocity, with peak exhalation speeds reaching as high as 100 feet per second. This creates a cloud of particles rich in virus that may extend out to as much as 27 feet. Some of this cloud may settle on nearby surfaces, and some portion will evaporate, producing aerosols. This may well result in contamination of ventilation or climate-control systems. While the participants in the M.I.T. studies were not masked, it appears that at least some of the high-speed ejecta from coughs and sneezes can make its way around even the best of masks. Indeed, one Chinese study found virus particles in multiple places in a masked patient’s hospital room, including air outlet fans and five bathroom sites (including the toilet bowl, sink, and door handle).
Are booster shots part of the answer? The Israeli experience suggests that the answer is an unambiguous yes. The United States has now committed to giving booster vaccines to all Americans. Germany and France have committed to giving boosters to older persons and persons with compromised immune systems.
Ontario has made a more modest commitment, agreeing to give booster shots to a relatively modest list of high risk persons, including long-term care residents, transplant recipients, those with hematological cancers, and those receiving certain anti-cancer drugs.
Experts are divided, however, on whether booster shots should be routinely given. Some scientists have claimed that the apparent reduced efficacy of vaccines over time may in fact be a cross-sectional, and not a longitudinal variation, which is a fancy way of saying that the vaccines simply aren’t very effective against Delta. Those who stake out this territory base their view not on the unambiguity of the data, but rather the ambiguity of the data; i.e. the inability to extract robust statistical conclusions pointing the finger at one cause or the other. In my view, it is a counsel of folly to wait until we have stronger statistical results. The various costs associated with another aggressive wave of Covid are too great to simply stand by and wait for better data. Put another way, the cost of a booster campaign that turns out to be unnecessary is far less than the costs associated with taking a plunge back into the darkest days of Covid because of the absence of a booster campaign.
The moral of the story? Covid is an unsympathetic pathogen, and it is not about to fold up its tent and go away anytime soon. Whether the renewed tsunami of Covid cases in various parts of the world is a product of the waning efficacy of the vaccines over time or their reduced effectiveness against Delta, or some combination, we are far from out of the woods. Either way, Canada is in for a rough ride this fall. And this is to say nothing of the risk that new strains will emerge (especially from under-vaccinated third world countries) that are vaccine-resistant, more virulent than any of the current crop, or both. Particular attention should be paid to those over 65 and those with compromised immune systems, who should be allowed to work remotely whenever possible. Complacency is simply not an option.
