Pandemic only accelerates among the unvaccinated

Santa Coloma de GramenetUmpteenth rise in the curve of contagions in Catalonia. This time, however, only among people who have not been vaccinated or are not fully vaccinated. Around 90% of the cases from last week have occurred among age groups that have not yet been offered a vaccine - three in five are under 29- or who have started vaccination but have not yet acquired immunity (aged 30-49). On the other hand, from the age of 50 onwards, incidences continue to fall steadily.

With 66% of those vaccinated with the full schedule, infections among those in their fifties have plummeted to 4% of weekly cases. Infections are also anecdotal for the over 70s (2.5%) and, according to data from the Department of Health, the only band that slightly increases its incidence is the one that goes from 60 to 69 years (3.5%). In this case, more than two thirds of those vaccinated have not yet received the second dose and around 15% seem reluctant to be vaccinated or at least to receive the AstraZeneca vaccine, since they have not received a jab at all.

Thus, the coronavirus epidemic in Catalonia is now running at two speeds. One of the curves continues to grow and mainly affects people under 49, who have a lower vaccination coverage. The other, which corresponds to those over 50, most of whom are fully vaccinated, continues to decline. "If the explosion in cases among young and unvaccinated shows anything, it is that vaccines work," says Clara Prats, a physicist and researcher at the Computational Biology and Complex Systems Group (Biocom-SC) at the UPC.

Prats is cautious and admits some concern about the drift of the epidemic in young people. She recalls that last summer it was already seen that transmission increased among young people due to the greater social interaction among them. And, unlike last year, in addition, now there has been the "perfect cocktail" for the virus to spread more easily and there is a boom in cases among young people: there is an increasing presence of the delta variant -more contagious- and many of the restrictions have been eliminated, including compulsory use of masks outdoors.

A clear example is the huge outbreaks that have originated in the Balearic Islands and the Canary Islands due to different end-of-year trips in which young people from all over the State took part. They have already caused over 353 infected students and 2,234 close contacts in Catalonia.

The Department of Health wants to open up vaccination for the under-30s "quickly" and at once. "But even if the youngest could start being vaccinated today," says Prats, "it would still take weeks to see the effects of vaccines on cumulative incidence". On average, it takes a month after the first jab to begin to see the protective effects of the vaccine in immunized groups. For example, the population aged between 40 and 49 years, which has only been vaccinated for fifteen days, has already achieved 60% of vaccinated with the first dose and will soon begin to see the drop in cases.

In the case of the population between 30 and 39, despite having already 18% of the population vaccinated with the first dose, they still represent one out in four weekly infections. For this reason, the Biocom requests "an immediate reduction in super-propagator events with many contagions" to avoid risk environments, such as large meetings, parties and unmasked gatherings indoors, which may hinder the vaccination process. At the moment, they say, there will be a "strong growth" in the coming days, but it will not be until the data from Wednesday and Thursday that you can have "a clearer idea" of the evolution. For example, if the rate of contagion (Rt), which indicates whether the pandemic is expanding, rises to 2 or not. It now stands at around 1.3.

Few young people admitted

The increase in transmission in younger age groups is occurring mainly in Barcelona, which accounts for a third of the country's infections. Within the Catalan capital, the western area is the most affected, specifically the districts of Sarriá-Sant Gervasi, where up to four primary care centers now detect twice as many cases as last week, and the Eixample. The trend, however, is reproduced throughout the country: of the 95,500 antigen and PCR tests carried out by primary health care on suspected cases, 5.5% are coming back positive. In the case of young people the figure soars to 8.8%, and in the case of those over 49 it falls to 2%.

Prats warns that primary healthcare could end up being saturated: "On the hospital side we are calm, because we have enough room to grow and take on the cases we need, but primary healthcare might again be subjected to a situation of great pressure. Primary healthcare is not only responsible for the detection of positive cases, the researcher stresses, but is also carrying out the vaccination campaign, tracking close contacts with epidemiological surveillance services and attending many other pathologies, whether chronic or acute, its assigned population may be suffering.

The increase in juvenile infections is not having an impact on hospital pressure for the moment, since most cases are mild or even asymptomatic. Today there are 467 covid patients in conventional wards - accounting for 4.3% of all hospital patients - and 136 in intensive care units (ICU). That is, one in five critical care beds is occupied by patients with coronavirus. Although this Monday there has been a slight upturn in the hospitalizations data, none of the five new admissions correspond to under-29s.

Catalan government spokeswoman Patrícia Plaja has explained that all new patients are aged between 42 and 62 years and that only one had received the first dose of the vaccine. The rest had not been vaccinated despite having been offered a vaccine. The problem for hospitals now is those reluctant to get vaccinated who belong to vulnerable groups. "Not getting vaccinated is assuming a situation of vulnerability that is avoidable," says the co-director of the coronavirus group of the National Center for Biotechnology and the Higher Council for Scientific Research (CSIC), Isabel Sola.

In fact, young people also get sick and are admitted to hospital. Clara Prats recalls that, at the European level, approximately two out of every hundred young people between 20 and 29 end up in hospital and, although much more unusual, some of them may end up in the ICU. "Young people are not immune to hospitalisation, there is no such thing as zero risk, but they are obviously less at risk than a person aged 60 to 69," she says. Following the same European data, this age group that is not yet fully protected would be seven times more likely to enter the hospital. "Now, if we approach the thousand of infections only among young people, as it seems that it could happen soon, it would mean that up to eighteen young people could be admitted daily to a health center for covid," Prats reckons.

Sola also points out that with covid there is a clear relationship between age and severity of infection -younger people face a smaller risk of getting sick-, but recalls that there are people who are not hospitalsed and are rendered unfit during or after infection. "For example, suffering persistent covid, especially young people. Exposure to the virus is like Russian roulette," she warns