Coronavirus
Society 01/12/2021

Mandatory quarantine for Omicron close contacts - even if vaccinated

New variant has been circulating in Catalonia for a fortnight and the Health Department says it is more concerned about increased transmissibility than gravity of infections

3 min
A female traveller on arrival at El Prat airport

Santa Coloma de GramenetOmicron variant could have been circulating in Catalonia for a fortnight, according to the Department of Health's analysis of wastewater. And what most worries health authorities is not so much whether it causes more severe infections, but whether it facilitates infection and has more ability to circumvent the protection afforded by vaccines. "We assume that it has greater transmission capacity and that it could escape [vaccine-induced immunity], although it has not been proven reliably, but virulence is not an aspect directly related to the spike, the mechanism that allows the virus to infect the cell," explained Tomàs Pumarola, head of the microbiology service of Barcelona's Vall d'Hebron Hospital.

The microbiologist says Omicron variant accumulates over 30 mutations in the spike (i.e. the part of the virus that allows it to access cells) and that it is precisely these changes that have meant it has become a variant of interest and that all efforts are now focused on learning more about its behaviour and trying to identify cases. Pumarola used the example of the key and the lock to explain why it is important to monitor these mutations: the spike is the key that the virus has to open the cell door and infect it. If vaccines make it harder for it to enter cells, the virus will mutate and perfect its 'key' to enter cells, attach to them and infect them more effectively.

"When we vaccinate, we generate specific antibodies against the spike. If the spike mutates, which is what Omicron has done, antibodies will find it harder to bind and the protection offered by vaccines could be reduced," Pumarola summarises, who points out that this does not necessarily happen with natural immunity, that is, immunity acquired by contagion. However, the expert recalled that the birth of new variants will be a trend throughout the pandemic and that each time a new one appears its implications for transmission and severity of infection will have to be investigated, as well as the need to reformulate vaccines. Pumarola postpones, however, this last possibility. "We have been losing the protection of vaccines against infection, but not against severe illness. What we do not want is for people to end up in hospital," he explained.

As for the only two suspected positives of being caused by the Omicron variant, identified at the airport of El Prat arriving from South Africa, the microbiology service of the Hospital Universitari de Bellvitge has not yet finished sequencing the samples and has not been able to determine whether they contain the mutations of the omicron variant. However, the Health Department assumes omicron has arrived in Catalonia. In this sense, the Secretary of Public Health, Carmen Cabezas, wanted to emphasise that although there is a situation of alarm throughout Europe due to the Omicron variant, the epidemiological evolution in South Africa (where the mutation originated) is "very low" compared to other countries, including Spain and Catalonia. "We have to put into context all the information we have about the variant. For example, over there it is summer and although there is a rise in infections, the figure is lower," she said.

All Omicron close contacts to quarantine

Cabezas also stressed that this increase in cases has not affected South Africa's health system. "We will have to see if it displaces the delta variant in places where vaccination coverage is 80%. The situation is totally different from South Africa, where there is a low population density but only 25% of people vaccinated," agreed Pumarola. It should also borne in mind that the Omicron mutations make it look more like the alpha variant – which was replaced by the delta – than the latter, which is now predominant.

If the vaccine continues to protect against severe infection, it is not strictly necessary to reformulate the vaccines. The microbiologist believes that the administration of booster doses will be sufficient, although this does not mean that in the medium or long term it will not be necessary to modify current formulas, "as already happens every year with the flu jab", to adapt to the predominant mutation. "As I have always said, this is a very dynamic process because the variants that adapt best and are more efficient biologically predominate. What we have to do is minimise the risk by avoiding large transmissions from person to person and continuously monitoring the variants in circulation," he said.

Therefore, the Department of Health has announced that close contacts of people who may be infected with the Omicron variant will have to quarantine even if they are vaccinated. Travellers from southern Africa who test positive will be considered suspects of infection with the Omicron variant. On the other hand, fully vaccinated contacts of Delta patients will not have to quarantine. Instead, they must take a test and, if positive, isolate.

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