COVID-19 Epidemiology, Mitigation, and Omicron Subvariants

Traveling in an airport during COVID-19

Written by WorldClinic

April 21, 2022


Since our previous update, COVID cases in North America have started increasing again, but as we have been discussing over the last couple of updates, even CDC has joined the shift from a major focus on cases to a minor focus on cases and major emphasis on severity and impact. Without regard to what the data is telling us, most people know from their own experiences with friends and family that the real number of cases feels comparable to almost any high caseload period during the pandemic. But we have no idea what the real number is because a much-reduced proportion of people are reporting positive cases. They either aren’t bothering to test because their symptoms are relatively minor cold-like symptoms and they do not want to be excluded from work (and this is especially true for hourly workers) or, even if they do test, they are using a home test and, even if their jurisdiction accepts home test results (which many do not), they don’t bother reporting their results.  So that moves the emphasis on how we track COVID squarely to hospitalizations – a number that’s much more standardized, although still imperfect. Hospitalizations have declined in the US although fairly stable over the last couple of weeks. Part of the reason that the number has stabilized is that many areas are reporting that older patients are often remaining in the hospital for longer than needed because nursing homes are short-staffed and unable to accept new patients. This makes the already low hospital numbers even lower in reality, but also means that getting back to normal flow from hospitals to non-hospital care facilities (for all purposes, not just COVID) is going to be disrupted for the foreseeable future as another consequence of the national shortage of hourly workers. We’ll leave the causes of that problem to the political classes, but the answer is not COVID – at least not directly. Deaths are similarly at very low levels; in fact, the lowest levels since the COVID-specific death data has been tracked.

In Europe, cases are at about a third of the original omicron peak in January and slightly above half of the BA2 peak last month. Deaths are at less than 20% of their peak and rapidly declining. There are a couple of hot spots, notably Finland and to a lesser extent Germany, but of the two, only Finland is in an uptrend. Trends in Asia and the Middle East are similar to Europe, although China asserted earlier this week that it had regained control over spread, then early Thursday reinstituted a number of controls as further spread was noted in Shanghai. The three hot spots other than China are Taiwan, Bhutan, and Thailand. Korea, Japan, Singapore, and Hong Kong are all in control, although India has seen a BA2-related increase in cases in Delhi and the surrounding areas and has reinstituted a mask requirement in public places. Conversely, Israel noted on Wednesday that it is dropping indoor mask requirements as of Saturday. In Africa, only Botswana is seeing significant issues

Omicron Subvariants

This finding in Botswana is worthy of mention as there is evidence that this could be due to new omicron subvariants, BA4 and BA5. So far, there has not been a significant spread outside of Botswana, but recall that the original omicron strain originated there, and then caused large numbers of new cases, albeit without large hospitalization increases, in South Africa before it spread to the UK, US, and Europe and the rest of the world from there. While BA4 and BA5 appear to be more infectious than BA2, this region of the world was not significantly affected by BA2 as most of the rest of the world has been. It may be that areas that were hit hard with BA2, which would include Europe, the UK, and North America, have enough resistance that BA4 and BA5 will not be able to get a foothold. So, for now, at least, these new sub-variants do not appear to be a near-term threat to areas that have been affected by BA2. This does bear watching, however, as they could follow the spread pattern of the original omicron. Speaking of variants, in Europe and North America, the focus now is on a “sub-sub-sub-variant,” Ba2.12.1.  Yes, it may be more infectious than previous omicron versions, but no more severe and possibly even less potent than earlier omicron. In other words, even more like other coronaviruses that cause the common cold in most people, but can be problematic in those with significant risk factors.


As most areas of the world are shifting in mindset, even if not by official pronouncement, from pandemic to endemic, what does that mean for day-to-day life? We reviewed this two weeks ago, noting that for the foreseeable future, it means that you should keep in mind the layered approach to infection prevention, considering the risk factors for yourself and those around you, and make your own judgment as to which layers of protection make sense for you. Immunizations, including at least the first booster dose, should still be considered the base layer of protection. We have previously discussed that no vaccination is completely risk-free, but in most cases, the vaccine-related risk is much lower than even the low risk of infection, especially since we are finding new COVID-related chronic issues, such as a noted statistical increase in type II diabetes in some at-risk people who had COVID. One other vaccine-related note is that cumulatively over the course of the original omicron wave, unvaccinated children aged 5-11 were hospitalized at more than double the rate of those who were vaccinated at 19.1 versus 9.1./100k – still small numbers, but much higher than the observed immunization serious side-effects risks.

Back to the mitigation layers: The next layer is avoidance of crowded indoor gatherings, followed by utilization of a high-quality mask, defined as a well-fitting N95, KN95, KF94, or similar. The effectiveness of these masks in reducing infection has been estimated at as high as more than 90%, but only while you’re wearing the mask. Screening testing has become hotly debated, with very risk-averse groups saying that they don’t care about the lower positive predictive value of tests in an environment with low infection prevalence, while others note that this higher false-positive rate unfairly takes people out of work, school, and other activities often for no true infection and that tests should be reserved for those who have symptoms or close exposures. We generally fall into the latter group, except in settings like hospitals, nursing facilities, or when you need to be around significantly at-risk people where even omicron infections can have more significant effects.

Mask Mandates

The big confusion right now is how to react to a court saying that the US Government does not have the authority to institute a mask mandate for public conveyances. Should this be appealed, as the Biden administration indicated on Wednesday night that they were going to do, the government would likely win as the 1944 Public Health Service Act is fairly broad in the powers given to the US Public Health Service for the prevention of communicable disease in interstate transport. That being said, putting masks back on is going to be like stuffing the genie back in the bottle, and should the government go in that direction, it’s likely that the reputation of the CDC will be further tarnished in many people’s eyes.

But let’s say that the mask requirement remains lifted, what should you do? If you feel that because you are fully vaccinated and are either boostered or you have had covid and are therefore at low risk for any significant illness, you will probably choose to drop masking in any environment where it is not required. This means you are at risk of catching COVID, just as you are at risk of catching the flu or many other viruses. For right now, COVID is still a somewhat higher risk than any of those other infections, but no longer orders of magnitude greater risk. The next level up is someone who understands the risks and is willing to accept some risk but still would like to minimize their chance of even a mild infection. For these people, they can feel comfortable removing their masks on a plane anytime the engines are running. Modern airliners have HVAC systems that very effectively both filter and turn over the air in the cabin, but the engines have to be running for that to be the case. So, people who are moderately risk-averse should keep wearing the highest quality mask that they find comfortable from the time they are in a crowded terminal through boarding and until the airplane has pushed back from the gate and started the engines (reversing that on landing). People who are not at all risk-tolerant should treat an airliner the same way they treat any public indoor environment: If they mask in their local grocery store, they should mask on the plane. This guidance does not cover every situation or level of risk tolerance, but it should give a good range of approaches.


Lastly, this week, a quick update on vaccine developments. Both Moderna and Pfizer have recently announced positive results on reformulated vaccines that more directly target omicron and its subvariants. This means that boosters for the start of respiratory disease season in the fall could directly target omicron. While the jury is still out on whether boosters will be needed, in our opinion, this makes it more likely that they will be advisable. Also, this week, Novovax provided preliminary data on phase 3 testing of their combined COVID/Flu vaccine with high rates of protection against all circulating strains of COVID and even higher levels of antibodies against common flu strains than with standard vaccines. It is still too early to decide which vaccine route will be the best way to go, but we should have much more data between now and then.



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