Omicron:  The pandemic lurches on.  Just when we thought that we were coming out of the woods, we are now in a 4th wave.  Case counts were dropping nationally but started to rise at the end of October, presumably as a result of the Delta variant.  Connecticut followed this trend starting in mid-November.  Here in Windham county (with the highest counts in the state) daily case counts were into the mid-20’s per 100,000 people about 5 weeks ago and are now close to 100.  As of a few days ago, Rhode Island was the national leader in case counts per 100,000.

The Omicron variant, with its unusually high number of mutations, is even more easily transmitted than the Delta variant, resulting in a doubling of cases every 2-3 days in the countries where it is better established and better studied.  The current vaccines are less effective against it, although protection against serious illness, hospitalization and death appears to still be good.  There do appear to be more symptomatic breakthrough cases, however.

Early assessments of Omicron-caused disease severity tend to suggest milder disease, but this assessment is far from certain and cannot yet be relied upon.  Given the currently over-stressed state of hospitals in areas with high case counts from the Delta variant, even a modest increase in hospitalizations due to the Omicron variant could have drastic consequences.

There is already a move to close entertainment events, limit restaurant and bar hours and it seems likely that further restrictions are coming.

If Omicron proves to cause mostly mild disease, and if it spreads widely as expected, then “herd immunity” is more likely to be achieved.  This will move us closer to an equilibrium point where, like influenza, the illness is common and usually mild and with relatively few people with long-lasting effects, hospitalizations, or death’s related to the disease.

Boosters:  As noted above, Omicron has confused the picture.  Studies conducted in the United States regarding vaccination showed significant loss of circulating antibody levels from (“humoral immunity”) at around 5-6 months (pre-Omicron) to about 55%, but with wide variations between individuals.  This was not true in studies done in the United Kingdom or in Canada, where 90% effectiveness was maintained.  The other path of immunity is “cellular immunity” mostly relating to T-cells, a type of lymphocyte which form in reaction to the vaccine (as well as in actual disease) and which are also important in the immune response.  Boosters definitely raise the levels of circulating antibodies and should therefore promote better protection.    In the end, a decision to take a booster shot follows the same logic as for the first dose.  Prior bad reactions to the vaccine would of course have to be considered.

It must be noted that for the Delta variant, and probably also for the presumably very soon-to-be dominant Omicron variant, vaccination does not prevent the transmission of the virus within a household.  In that instance, as contact is more between family members is closer and more prolonged , and with higher viral loads found in the Omicron variant, the likelihood of viral transmission is significantly increased.  If a family member is vaccinated, but brings the virus into the house, they will still initially transmit a lot of virus, but the viral load falls off more rapidly as compared to an unvaccinated person, therefore shortening the period of contagiousness.

Home Testing:  At least up until now, testing for Sars CoV-2 did not change when variants emerged, and that will probably not change with the emergence of the Omicron variant.  Home testing has the possibility of being very helpful for those of us who wish to avoid infections or at least to limit their spread.  Availability of tests seems to have improved, but demand is very high, and likely to get a lot higher.  It is possible that supplies will be diverted to hospitals, medical clinics, and large employers in order to maximize the impact of testing in the face of inadequate supply.

The “gold standard” for testing for the presence of the virus is finding viral DNA (so-called PCR testing).  That type of test requires a laboratory tes, is expensive, and the results may come after delays that make them less useful for planning family events.

Home tests detect viral proteins (“antigens”) other than DNA, and give results much more quickly and much less expensively.

The following information, (gleaned largely from an article in the October  12, 2021 issue of the Journal of the American Medical Association) should also hold true for the Omicron variant.  The information is the most specific for the Abbot BinaxNow test, but should be similar for other antigen tests now on the market.

Beside availability and cost, the two most important aspects of home testing and the accuracy of the results are:

  • Sensitivity: If I have the disease, how likely is it that the test will give me a positive result.  A test with high sensitivity correctly identifies “true positives” and minimizes “false negatives”.
  • Specificity: If the result is negative, how likely is it that I don’t have the disease?  A test with high specificity minimizes the rate of “false negatives, or people who have the disease but test negative.

Ideally, we want a test which has both high sensitivity and high specificity.  But this is somewhat unusual in the general universe of tests.

The most accurate results from testing for COVID-19 with the current tests are obtained firstly when the specimen is collected properly, and secondly that the test is done at the appropriate time (not too soon, and not too late).  It is important to distinguish between testing people who have symptoms, as opposed to those who do not (“asymptomatic”).

  • The specimen must be collected properly, which will often involve some discomfort. Detailed instructions are included in the test kit packaging, and there should be a web address given for a video which demonstrates the technique.  This is a critical step.
  • The Delta variant produced fever, flu-like symptoms, cough, headache and significant loss of smell and taste. So far, Omicron disease is not nearly as likely to produce loss of smell and taste, and fever is not as prominent.  In Omicron, runny or stuffy nose, dry cough, sore throat and fatigue are common.  If you are symptomatic   transmission has already begun, about 2 days before the onset of symptoms, and continues for about 5 days.   In other words, if you are symptomatic, you can test immediately.  The tests are highly sensitive for symptomatic persons, especially if the viral load is high.  False negatives are still possible.
  • However, even if you are infected, the viral load decreases fairly quickly, and testing after 5 days of symptoms is unreliable. A negative test at that point may then be a “false negative.”
  • If you are symptomatic, and receive a negative test, especially late in the 5 day window, or shortly afterwards, the result should either be confirmed with a PCR test if possible, especially if you know that you have been exposed. A less precise but still useful alternative is to have a 2nd rapid antigen test (which logically should be done soon after the first negative test, again being sure to collect a good sample.
  • If you are asymptomatic the earliest useful date for testing is the second or more likely the third day after exposure, but if you are destined to remain asymptomatic the viral load will decrease more quickly and a second test should also be done fairly quickly, probably a day later.
  • It is thought that asymptomatic persons tend to wait longer to be tested, and so it is possible that the window of opportunity may pass quickly. If they were infected however, the viral load would also be low and they would have been less likely to transmit the virus to others.  But there will be uncertainty remaining in this instance.

Rapid tests can be useful, but as you can see do not always give reliable information.  They are clearly better than no testing.

In conclusion, the next few weeks should see a clarification of the presentation and severity of the Omicron variant.  I will keep posting as circumstances warrant.  Please don’t give in to despair and throw caution to the winds as some have done.