COVID-19 Epidemiology, Testing, and Treatment

Written by WorldClinic

December 31, 2020


Unlike where The United States stood just two weeks ago with just about every state seeing rapid increases in case numbers and hospitalizations, the case numbers and deaths are actually decreasing in almost the entire country. As of Wednesday, only three states, New Jersey, New York, and Delaware are seeing case counts that are increasing on a week over week basis, and 36 states are seeing double-digit percentage-based declines in case numbers. However, case counts are not necessarily the best statistic at which to look, and the quality of the data leading up to the extended Christmas holiday introduces some questions into the analysis. In fact, over the last two days, the daily case numbers are back up to near where they were at the peak two weeks ago. Still, many of the epidemiological models are beginning to agree that the United States is, in fact, at or near the peak number of cases. Deaths are also decreasing, although hospitalizations continue to increase on average across the country.

In Europe, cases are down roughly a quarter from the peaks seen in October but have plateaued over the last month. Decreasing cases on the continent of Europe have been overwhelmed by a significant increase in cases in the United Kingdom. There is a significant concern that this increase in cases may be due to a new strain of SARS CoV2 that may be more infectious than the existing strains. While the news portrays this as a clear fact, the reality may not be quite so clear. Basic Epidemiology tells us that the most efficiently infectious strain becomes the most predominant, but at the same time, there were observed behavioral changes in the United Kingdom with significant travel and increasing pandemic fatigue noted, much of which was associated with the Christmas Holidays. In any event, this bears watching, but, importantly, this new strain does not appear to be associated with an increase in disease severity or death and does not appear to be less susceptible to the vaccines.

In Asia, specifically Singapore, Hong Kong, and Japan, there is a growing concern about rising cases. The shape of the Japan epidemic curve looks strikingly like the US curve, but when you look at the scale of actual case numbers, Japan is at least an order of magnitude less on a per capita basis, and Japan is beginning to see evidence of flattening of their curve. Singapore is also concerned about a rapid increase, yet their case rate continues to be well less than one case per 100,000 per day, and while Hong Kong returned to near crisis management mode over the last month, The overall case count per capita in Hong Kong still hovers around the nearly negligible one per 100,000 per day, with a decreasing trend over the month of December.

Aside from cases, the most important epidemiological discussion over the next several months will be herd immunity. Estimates of the proportion of required natural or vaccine-induced immunity to reach herd immunity have ranged from well less than 50% to as high as 90%. Dr. Anthony Fauci of NIH has given estimates that have ranged from the 60% to most recently near 90% to reach herd immunity. Dr. Fauci has acknowledged that his estimates of immunity are influenced by the message that he is trying to portray on the importance of prevention including immunization. In other words, politics plays a role in the communication of science. Unfortunately, the bottom line is that we are not going to know what is really needed for herd immunity except in retrospect. At the same time, however, even if we do not reach true herd immunity, we will reach a point where there are fewer and fewer susceptible people in the community which will lead to decreased infections, even if not enough decrease, initially, to put a complete stop to the epidemic. But as we do get immunizations to the most vulnerable and the most exposed, that, by itself, will effectively decrease the impact of the epidemic to something similar to a bad flu season thus removing the justification for keeping the economy on partial lockdown.


There are no significant new updates from two weeks ago. We still expect to have a home antigen test that will be available for purchase in early January, but the basic testing environment remains the same with PCR tests remaining the relative gold standard and antigen tests having their place primarily for the more rapid diagnosis of someone exhibiting symptoms of COVID-19. On that last point, the United Kingdom had planned to field large-scale antigen testing across the country to use screening to help keep down overall case numbers. The week before last, however, the health authorities in the UK determined that the accuracy of antigen testing in an asymptomatic population, including both false negative and false positive rates, is unacceptable and they canceled plans for mass antigen-based screening. In thinking about any screening program, it is important to remember that at best a screening program results in some degree of risk reduction and not risk elimination. With that in mind, instituting a screening program may be reasonable in certain circumstances. With the growth and availability of saliva-based PCR tests that make testing relatively easy and fairly reliable one day turn around, If a group or organization does elect to risk reduction through testing, then saliva-based PCR testing would be the leading choice.


There are no new treatments. But some interesting patterns have developed in the utilization of the treatments that are available. It has become clear that the anti-viral Remdesivir treatment and the various antibody treatments are most effective if applied in the first few days after diagnosis. An issue is that even those people who are going to become seriously ill, typically do very well in the first few days after diagnosis, making it difficult to determine who will benefit from the use of these advanced therapies. In fact, the use of monoclonal antibody treatments has been a fraction of the projected use. What is happening is that most people are being managed by their primary care physicians while they are doing very well in the first few days after diagnosis, and since it is difficult to predict who will benefit from these treatments and because these primary care doctors are not comfortable with the use of these infusion-based therapies, few patients receive them. For someone who is statistically at low risk – generally meaning someone below 60 years of age without other significant medical issues, this is totally reasonable. But for anyone who is older or does have other medical issues, it is important to have a discussion with your physician early while potentially still feeling well and decide whether the use of Remdesivir or antibodies or both may be beneficial. If you are somebody with risk factors, do not put off that discussion just because you are not feeling any sicker than you do with the case of the flu. This is something to be aggressive about even if your primary care provider is not.


We are now a little over 2 weeks into the beginning of vaccinations with the Pfizer and BioNTech mRNA vaccine, and about a week into vaccinations with the Moderna mRNA vaccine. There have been issues with allergic reactions, possibly somewhat higher than with other vaccines, but not too significantly different than others. If you are to receive either one of these vaccines, it is important to make sure that the vaccinator or vaccination location has the skills and equipment necessary to manage an allergic reaction, but that is no different from any other vaccination.

As of Wednesday morning, in the United States, about 12 1/2 million doses of coronavirus vaccine have been distributed with about 1/4 of that already administered. As was likely predictable there has been significant tension developing between trying to get needles in arms as rapidly as possible while still doing this in a way that complies with the prioritization schema. News reports of people getting the vaccine out of their priority order have caused some states to ratchet up the bureaucracy associated with administering vaccines which has served to slow down the vaccination process. On one hand, nobody wants to see people jumping the line, but, unfortunately, even well-meaning providers are being threatened with administrative or even criminal sanctions if they cannot adequately document the compliance of every vaccine dose that they give with the priority schedules. The net result is that vaccines have been limited primarily to the large healthcare systems that have the appropriate tracking systems already in place, with less progress made in getting vaccines into the hands of pharmacies and individual providers who are most well-positioned to immunize larger parts of the population. Right now, these kinks are being worked out of the system and the rate of vaccination is beginning to ramp up. The phase one high risk or high exposure groups are on schedule to be vaccinated over the course of January, moving to essential personnel through February and into March and then beginning more general parts of the population late March and into April. This is an optimistic view of the situation, but with the current demand from the general public, the state authorities are going to be more aggressive in getting vaccinations out to their citizens.

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