The wildfire spread of the Omicron variant of the coronavirus and the apparently lower severity with which it manifests itself in vaccinated people are pushing many countries to relax the rules on quarantine. Are these decisions founded from a scientific point of view? The short answer is: probably not. Let’s see why.
Too many “absent”. In the UK, the period of isolation (more correct term than forty) for the vaccinated positives it was increased to seven days, from the previous 10; in the US, the quarantine for asymptomatic positives has been shortened, despite the contrary opinion of many scientists, to five days. In Italy the period of exclusion from social life for the infected it is 10 days for the unvaccinated or recently vaccinated and seven for those vaccinated with booster (the third dose) – provided that a tampon certifies, in both cases, the negativization (Who the rules in full). But there is a lot of pressure to streamline the quarantine on the US model.
The motivation is purely economic. The new wave of infections has spilled over a population now largely vaccinated, therefore better protected from the most serious outcomes of the disease, with the exception of the frail. However, it made itself felt on the organizational level: since Omicron is able to easily “puncture” vaccines, which are less effective against infection, among the infected and close contacts the workers of many essential services have disappeared. Hence the decision to shorten the quarantine.
Critical days? Third to sixth. If we analyze the typical behavior of the virus, however, the short quarantine is of little use. According to a review of 79 studies on viral dispersion in infected people published in the journal Lancet Microbe and quoted by The Conversation, the peak viral load in people infected with the Omicron variant is between the third and sixth days of exposure to the virus.
The work including data on 5,340 patients took into account not only the viral load, that is, the quantity of viral particles present in the organism and detected by the molecular swabs even after the symptoms have recovered; also evaluated the ability of these human hosts to internally multiply and spread the virus, that is, theirs infectivity.
Typically we start with a couple of days of low viral load (which often escapes rapid swabs) to reach a peak between days three and six, a trailing between the seventh and ninth and the complete disappearance of the virus around the tenth day . All of this supports the need for a 10-day quarantine. A Japanese study still in pre-publication confirms that the peak of viral shedding in those infected with Omicron is between the third and sixth day of the onset of symptoms. Other works suggest a slightly shorter period of infectivity for asymptomatic people, but when it comes to national policies and a highly contagious virus, shouldn’t the rule of caution apply?
Free … at the most beautiful. Furthermore, according to a recent analysis by the University of Exeter (UK), one in three people who tested positive for Omicron would still be infectious after five days. Therefore, the shortened quaratenes allow a considerable number of potentially contagious people, and not only, probably at the peak of viral dispersion, to return to public life.
Quick swabs, which in many cases are sufficient to certify healing, are not always reliable. Especially if performed at home with procedures that are not always correct, they could give falsely reassuring results. And despite the recommendations for convalescents to avoid crowded places and wear FFP2 masks, the protection of the most fragile is currently entrusted only to individual common sense.