BREAKING! COVID-19 Seroprevalence: Only 5% Of The Population In Spain Found To Have SARS-CoV-2 Antibodies
: The Spanish ENE-COVID national seroprevalence study concludes that 5% of its population has antibodies. This percentage has hardly changed in the three waves of which the study consists: in the first it was estimated at 5% and in the second and third it was 5.2%, results that confirm that, despite the great impact of the pandemic in Spain, the figures are not high, which rules out the goal of group immunity in the short term.
Dr Marina Pollán, the director of the National Center for Epidemiology and scientific director of the study, Dr Raquel Yotti, the director of the ISCIII and Dr Faustino Blanco the secretary general of the Ministry of Health, , presented the results yesterday morning.
The announcement of the final results coincides with the publication of the study findings in the journal: The Lancet https://www.thelancet.com/journals/lancet/article/PIIS0140-6736(20)31483-5/fulltext#%20
Among the key issues analyzed in the study, carried out over two months, is the evolution of the antibodies, which was one of the objectives. An overall seroconversion rate (people who did not have antibodies in the first wave and who developed them throughout the study by having contact with the virus) of 0.9% between round 1 and round 2 has been observed, a somewhat lower percentage (0.7%) between round 2 and round 3. These figures reflect the low appearance of new infections after confinement.
Also, seronegativization has also been observed, that is, the absence of detectable IgG antibodies in people who previously had them, being globally 7.1% between round 1 and round 2, and approximately 14% when analyzing The entire period of the study, although this last data requires confirmation. Antibody "loss" was more frequent in people who had no symptoms (11.0% between rounds 1 and 2, with more accurate information) and much less frequent in participants with positive PCR (0.5 %) and in those who described sudden loss of smell or taste (2.6%).
The distribution and map of participants with COVID-19 symptoms (people with three or more symptoms or with sudden loss of smell) in the last two weeks of the study gives an idea of the most recent evolution of the epidemic. While the percentage of symptomatic patients has decreased substantially between the first and second round, a slight increase has been observed in the last round, which could be the result of the greater mobility of the population after the period of confinement. It is possible that a percentage of these patients may be cases of COVID-19 in the early phase of the disease. The monitoring of the participants may allow answering these questions.
The researchers consider that the results obtained in Spain, a country with an intense epidemic wave in which seroprevalence figures are low, reflect the difficulty of obtaining herd immunity in the short term. In this sense, the comment that accompanies the article in "The Lancet" by researchers from reference centers in Geneva (Drs Isabella Eckerle & Dr. Benjamin Meyer) points out that "it would be unethical to subject the population and the health system to increased pressure to achieve this group immunity."
Briefly these results, together with the
presence of a substantial percentage of asymptomatic infections, reinforce the need to maintain public health recommendations for social distancing, use of masks, and hand washing.
As mentioned in said publication, and as it has already been carried out in the dissemination of preliminary data from the first waves, there is considerable geographic variability in the percentage of seroprevalence. Some provinces stand at 2-3%, while others exceed 10%, registering the highest percentages in the central part of the peninsula. The percentage is also higher in population centers with more than 100,000 inhabitants compared to municipalities with a smaller population (6% and 4%, respectively).
Interestingly there are no differences between men and women and, with regard to age, the prevalence of IgG anti SARS-CoV-2 antibodies is slightly lower in children and adolescents (around 3.5%), with little variation in adults. The article published in 'The Lancet' also highlights the highest prevalence of antibodies in healthcare personnel (10%) and among workers in nursing homes and social healthcare centers (7.7%).
The final results of the study confirms that between 74% and 89% of the participants who reported having had a positive PCR at least two weeks before the study, IgG antibodies against the coronavirus are detected. Among people who report having symptoms compatible with the disease, seroprevalence increases with the number of symptoms and is particularly high in people who report sudden loss of smell and / or taste (40% -41%). Finally, it is confirmed that around 2.5% and 2.8% of the participants who did not report any symptoms presented IgG antibodies, which reinforces the existence of asymptomatic infections.
Also it was observed that participants who reported having had contact with a confirmed COVID-19 case, or with a person with compatible symptoms, had a higher prevalence of antibodies than the general population. The prevalence in people who have lived with a confirmed COVID-19 patient stands out, which is between 27 and 31% in the different rounds. Those living with people with symptoms compatible with the disease also had a higher than average seroprevalence (15%). In people who report having had contact with a confirmed case outside the home, seroprevalence ranges from 10% to 15% in the different rounds.
The study included a total of 68,296 participants, of which 54,858 have participated in the three rounds, representing an adherence of almost 90%. Additionally, 91% of participants have provided at least one blood sample for analysis.
A total of 186,908 rapid tests were performed (plus 9,755 in the island-specific study) and 165,176 blood samples were collected (plus an additional 9,130 in the island-specific study).
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