COVID-19 Epidemiology, Travel, and the Holiday Season

Travelers exiting a plane while wearing masks due to COVID-19

December 9, 2021


The issues this week continue to swirl around omicron, however, we still have very little hard data. Over the next week, we should be getting more good data and analysis but already we are beginning to get a few indications of the way things may go.

First, as we review what has been learned over the past week, keep in mind the paradigm of key factors we outlined last week. These key factors are: how infectious is the new variant, how severe is the disease that it causes, and how well are mitigation tools work against it. And specifically with regards to the mitigation tools, consider antiviral medications, monoclonal antibodies, vaccines, and protective measures such as masks, social distancing, and ventilation.

In the last 2 days, there has been some data-driven news. First, at this time last week, omicron had been detected in 1 US state. As of Wednesday afternoon, it has been detected in about 21 states, with a total of about 40 people. Of those 40 individuals, about three-quarters of them have been vaccinated, and all except 1 were only mildly ill. The primary symptoms amongst these 40 are similar to what is being seen in other parts of the world, a mild cough, congestion, and fatigue. These symptoms are similar to a simple upper respiratory infection, with a common cold. While 40 is a very small number, epidemiologists in South Africa are estimating the doubling time for the number of cases at about 3 days. Doctors in the United Kingdom have said that that seems about right with what they are seeing and expect that omicron will become the dominant strain in the UK in the next 2 to 4 weeks. While I have not seen specific estimates regarding when omicron will become dominant in the United States, it is reasonable to expect that delta will remain the dominant SARS-CoV-2 strain through the holiday period.

The most concerning news coming out of South Africa is that they are seeing a spike in hospitalizations. That does seem to indicate that omicron may not be entirely benign, but it is worth noting that the rate of increase in hospitalizations is still well below the rate of increase in cases.


The very first analyses of vaccine efficacy against omicron have started to come in from both Pfizer and Moderna. Both companies note that in initial studies, the indications are that anyone who is fully vaccinated with an mRNA vaccine appears to be effectively protected against serious disease or death. This is based on laboratory studies of how well the virus is neutralized by blood samples taken from people at various stages of vaccination. Unfortunately, these vaccinations do not appear to be highly effective at neutralizing the virus in the early stages of infection. This means that people who are fully vaccinated with an mRNA vaccine are likely at risk of getting infected and mildly symptomatic but not at high risk of serious disease. However, the findings from the 2 manufacturers went further to show that a booster dose did in fact create effective immunity against infection with omicron. Both manufacturers, however, cautioned that these statements are based on tens of tests, not the thousands that are needed to make definitive findings. Similar data from Johnson & Johnson has not yet been released.

With these findings, the United Kingdom today and over the next week is putting in place new restrictions in an attempt to reduce spread while they redouble their efforts to get boosters out to most people. While the United Kingdom was effective in their initial vaccine distribution, they have been behind in the uptake of boosters. This has been felt to be a major part of the reason for the continued ongoing increase in cases, most of which are due to delta, not yet omicron. The new restrictions in England include a direction to work from home if possible, a legal requirement to wear a facemask in most indoor public places, and displaying proof of 2 doses of vaccination in order to enter nightclubs or other places with large crowds.

However, this discussion of case counts may not be that important in the long run. If larger data sets do confirm the anecdotal findings and very limited data from South Africa and the United States regarding how mild these cases are, then it may be that we will stop focusing on transmission and case counts and look more at how to protect only the most vulnerable members of society and not worry about cases amongst younger people who are not endangered by the virus. Others may say, that having large numbers of people not at risk for bad outcomes infected with the virus raises the possibility of spreading the infection to people who are at risk or to younger children who are unable to get vaccinated. While that is true, young children are generally not at high risk of bad outcomes should they get infected, and most adults who are at risk are well protected by the vaccine, coupled with monoclonal antibodies and antivirals should they nonetheless become ill.


Speaking of monoclonal antibodies, analysis has been released in the last 2 days from Glaxo Smith Klein showing that their particular monoclonal antibody cocktail has demonstrated a small loss of efficacy, but that it is still generally very effective in combating the omicron variant. This is great news and answers one of the important concerns that we highlighted last week: will omicron render monoclonal antibodies ineffective. With regard to at least one of the available formulations, that answer is “no.” With regards to antivirals, both Merck and Pfizer, the 2 manufacturers of the current antiviral candidate medications, have indicated that they do not see significant antiviral resistance conferred onto the new omicron variant. In a news conference on Wednesday, the CEO of Pfizer indicated that they will be submitting the last required set of data to the FDA in the next few days. This data will show an 89% efficacy in preventing hospitalization when administered in the first few days after a COVID-19 diagnosis. He indicated that he believed authorization for emergency use by the FDA would be issued by the end of the month and commercial level mass production will move to distribution over the early part of January.


Getting to international epidemiology, Europe in the last two weeks has dropped its focus on case counts and is moving to a 0 to 10 score of level of concern based on a combination of infectivity and severity data. Using this about ¾ of Europe is in the high or very high level of concern category, with an average score in Europe essentially unchanged over the last 5 weeks. Currently, the hardest-hit countries in the EU include Belgium, Czechia, Germany, Hungary, the Netherlands, and Poland.

In Asia, case rates are climbing fairly rapidly in Korea, while Japan, Hong Kong, Singapore, and Australia remain stable at low levels. China continues to report almost no cases throughout the country. South Asia also continues to report low case numbers. India has expressed grave concerns about omicron but also hope that their summer outbreak may have been recent enough that the great bulk of the population maintains effective natural immunity.

Holiday Season

Now to some practical recommendations for the upcoming end-of-year holiday season. For areas of the world where omicron has not yet taken hold, especially the United States, the previous guidance regarding activities in the environment dominated by delta still holds. Holiday gatherings can be held at reasonable risk through the application of the Swiss cheese approach to protection. That means applying multiple layers of risk mitigation with the knowledge that no layer is perfect but with all layers applied risks of bad outcomes are greatly reduced. First, and perhaps most importantly, if you hold a gathering try to require that all guests are vaccinated and to the greatest extent possible have had boosters. Next, maximize ventilation. We know that as opposed to earlier versions of the virus the delta variant behaves like an aerosol. This means that the key feature is not time and distance but air exchange in the venue compared to the density of people. Next, if you cannot ensure that all are vaccinated then masks can be at least a moderate risk reduction for all. With delta, things that may not be so important are touchpoints and things like sharing utensils on buffets. This does not mean to ignore surfaces, but it is reasonable to think of them much as they would be addressed during a typical flu season.


Another area of concern is travel. For many of the reasons discussed previously, domestic travel, if vaccinated, is a low-risk activity. Yes, you should try to avoid packed crowded areas in the airport and during boarding and deplaning times. But travel has not been a huge source of transmission. This should also apply to international travel but with international travel, there are the administrative concerns of short notice or even no notice changes in border controls, vaccination, and testing requirements. Additionally, if you were to become infected abroad, even if your infection is very mild, you may find yourself stuck for 10 to 14 days extra in for an area possibly a very high expense just waiting for your isolation period to expire. If you are making international travel plans, make sure you have thought through this possibility.

Finally, for this week, something that we have not discussed in many months, what to do if you do find yourself with a positive Covid diagnosis. If you are a young healthy person, with no significant risk factors, then you treat this as any viral illness: Fluids and Tylenol and/or a nonsteroidal anti-inflammatory for fevers or aches and pains. Obtain a pulse oximeter and routinely check your oxygenation even if you feel you have no breathing issues early on so he can establish a baseline. No healthcare is typically needed unless the pulse oximeter shows drops into the low 90s. If, however, you do not have any risk factors at all, even if slight, you should get monoclonal antibodies. These continue to be easily administered and highly effective mechanisms for limiting the extent of disease and even shortening the course of the infection. Unfortunately, access to monoclonal antibodies can still be complicated, although almost all states provided a website that shows locations that are allocated monoclonal antibodies. It is important not to wait if you are somebody with risk factors, get this done as soon as possible. If you wait until you feel that you need the monoclonal antibodies, it is likely too late.

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