First round: Only 5% of Spaniards have antibodies against the coronavirus
Second round: Spain still lacks immunity against coronavirus
Third round. 11.7% of Madrid residents have passed the Covid-19
One in 10 Spaniards would have been infected with coronavirus throughout the pandemic, according to preliminary data from the fourth round of the
ENE-COVID seroprevalence study
, which reveals that the global prevalence of IgG antibodies against SARS-CoV-2 is 9.9% since the study began.
This prevalence is higher in certain groups, such as health personnel, with 16.8%.
This figure would be equivalent to that in Spain 4.7 million people have been infected, as explained by the director of the Carlos III Health Institute (ISCIII), Raquel Yotti.
In the previous round, it was estimated that seroprevalence was 5.2%
, that is, 2.3 billion people had been infected with the virus.
However, it must be remembered that the study does not take into account institutionalized people living in residences or in prison.
In this fourth round, carried out during the second half of November,
two complementary indicators have been used
: the current prevalence of IgG antibodies, which reflects the percentage of people with a positive result in the rapid test this round and allows comparison with previous rounds , and the global prevalence, which indicates the proportion of people in whom antibodies to SARS-CoV-2 have been detected in any of the four rounds of the study.
Thus, while the overall or cumulative prevalence would be 9.9%, in this round, 7.1% would currently test positive for antibodies.
The laboratory studies that are being carried out these days at the National Center for Microbiology of the ISCIII will make it possible to analyze whether the difference between the global prevalence and the current prevalence is due to the duration of immunity or other factors related to the techniques used.
In previous rounds, 14% of the people who had tested positive for antibodies were negative on repeating the test
.
It must be remembered that there are cases of infected with covid-19 that do not test positive for antibodies after the infection or have an undetectable level.
In this fourth round of the study, 51,409 people
from all the communities and the two autonomous cities participated, 77% of the invited participants, as detailed by Alfredo González, secretary general of Digital Health of the ministry, who has highlighted that it is a "A new milestone that places Spain in the few countries that can calculate the impact of the coronavirus with precision and rigor."
In this figure there would be a certain underrepresentation of children under 10 years of age, young adults and the very old, factors that have been taken into account in the population estimate presented in the report that shows the new data.
María Pollán, director of the National Epidemiology Center of the Carlos III Health Institute, acknowledges that "there were people who were tired of participating in the same study, others were afraid of missing work and others were very afraid of the epidemic," she explains. .
The geographical variability in the results is repeated, as highlighted, being greater in the Community of Madrid and Castilla-La Mancha and Castilla y León, although "now it has been possible to observe a high circulation in Navarra, Barcelona and Lleida within Catalonia and Zaragoza in Aragon ".
In other words, the study shows a greater dispersion of the epidemic wave in Spain.
By provinces,
Cuenca, Soria and Madrid have an accumulated global seroprevalence of 18%
, while it is less than 5% in areas such as the Canary Islands, Valencia, Huelva, Córdoba, Pontevedra, Coruña and Lugo.
In any case, to questions from journalists, Pollán recalled that even in the areas with the highest seroprevalence, the so-called herd immunity would still be a long way off, which the experts estimate in the best of cases at 40%.
"It must be remembered that the first case of reinfection, which also infected other groups, occurred in Madrid," he said, adding that therefore the greater seroprevalence should not invite to ignore the protection measures.
The percentage of seroconversion, that is, the seronegative people in the first phase of the study who now have detectable IgG antibodies is 3.8%, a percentage higher than the 0.7-0.9% detected in the first rounds ,
which Pollán considers that it reflects "all the mobility of the summer and the autumn"
.
The percentage of asymptomatic people during the 4 rounds who have IgG antibodies is 3.3%;
in the previous rounds it remained between 2.5 and 2.8%.
The percentage of asymptomatic patients in relation to the total number of positives is estimated to be around 30%.
In which groups is there the greatest incidence?
With regard to active workers, Pollán has highlighted that there are a series of groups with a higher incidence: health personnel (with 16.8%) and women who care for dependents at home (16.3%) present the highest figures for global prevalence.
The global prevalence is also significantly higher in women employed in cleaning tasks (13.9%) and in women workers in the social and health sector (13.1%)
.
It would also be 13% in the foreign population, although it is unknown if it is attributable to the type of work they do or their living conditions.
On the other hand, people who have lived with a confirmed case at some point have a 31% prevalence of IgG antibodies in this fourth round;
it has been 13% in the people who have had contact with a confirmed non-cohabiting case.
In addition, the seroconversion rate among participants who since the summer have lived with known or suspected cases of COVID-19 is multiplied almost by 10 with respect to the global percentage of seroconversion:
it stands at 35% in cohabitants with a confirmed case and a 26.3% in cohabitants of people with COVID-19 symptoms
.
The new ENE-COVID data confirm that the prevalence increases with the number of symptoms compatible with COVID-19, and that it is particularly high (43%) among those who lose their sense of smell, one of the most specific symptoms of the infection.
Diagnostic capacity has improved
Those responsible for the study recall that when the previous rounds of the study were completed, in which a 5% seroprevalence was estimated and compared with the confirmed cases, it was observed that only
1 in 10 cases of SARS infection
had been
confirmed- CoV-2
.
In this second epidemic wave, it is estimated that the detection percentage can reach 60%, that is, approximately 6 out of every 10 infected patients would be identified as confirmed cases.
In this sense, Yotti has emphasized "the use of antigen tests has been fundamental" to improve this diagnostic capacity and
early detection in the case of people with symptoms or contact with a positive
.
However, it has made a call to use them properly, alluding to the population screening carried out by various autonomies, which are discouraged by professionals and the manufacturers themselves due to their lower sensitivity in asymptomatic patients.
The director of ICSIII has indicated that it is not planned yet when the fifth round of the study will be.
They will wait to consolidate the results after the laboratory tests, see the epidemiological situation and also adjust to the future vaccination campaign against covid-19.
González has reiterated that, once the first is authorized, the Ministry of Health is preparing the device so that immunization occurs at the same time throughout Spain.
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