Key Findings of Spain’s Macro Coronavirus Study: 5% of Spain’s Population Has Antibodies But It’s Far from a Herd Immunity

Does the coronavirus affect more men than women? Are there certain regions which have seen a more expansive spread of the virus? Here are some of the conclusions that the first wave of the seroprevalence study in Spain have revealed. 

THE preliminary results of the seroprevalence macro-study show that 5 per cent of the population, 2.3 million Spaniards, have been in contact with the virus, which is almost 10 times more than those diagnosed by PCR, which places the country very far away from having developed a herd immunity.

However, this is a conclusion based on data from the first three waves of the investigation which were carried out between April 27 and May 11.

How does the study work?

So far, 60,983 people have participated in the national sample. Out of this sample, 96 per cent are Spanish nationals, 48.4 per cent (29,255) are men and 51.96 per cent are women (31,642).

The preliminary results from this first wave have only been conducted via the rapid tests, however the study will also incorporate laboratory analysis.

The results of the test have shown that the estimated prevalence of coronavirus antibodies in Spain is currently 5 per cent, which is equivalent to around 2,350,000 Spaniards who have contracted the virus. This is almost 10 times more than the 229,000 diagnosed by PCR that appear in the statistics of the Ministry of Health.

However, this also means that the lethality of the virus, which current statistics from the Ministry of Health show to be 11.9 per cent are reduced to 1.1 per cent in the results of the macro study.

The results also show that there are hardly any differences between sexes as it is just as common in men (5.1 per cent) as it is in women (5 per cent).

By age, the prevalence is lower in babies, children and young people, and is more stable in older groups: amongst the 268 children tested under one year of age, the prevalence is 1.1 per cent; in the 1,693 children under the age of five it was 2.2 per cent and for the 2,857 between the ages of five and nine, the prevalence was 3 per cent.

When looking at the prevalence across careers, 6.3 per cent of essential workers have antibodies; as well as 6.1 per cent of pensioners, 5.8 per cent of active workers, 4.5 per cent of domestic workers, 4.2 per cent of people with work disabilities, 3.7 per cent of charity professionals, 3.6 per cent of students and 3.3 per cent of unemployed people.

The greater the number of symptoms individuals have experienced, the greater the prevalence of antibodies. For individuals who have experienced between three and five symptoms, the prevalence is 8 per cent, more than five symptoms elevate this to 14.7 per cent, and amongst those who have lost their sense of smell this prevalence shoots up to 43 per cent.

There is also a great difference between prevalence and geography: 1.1 per cent prevalence in Ceuta, but 14.7 per cent in Soria. Most areas in Castilla-La Mancha and Madrid show figures higher than 10 per cent.

In municipalities with more than 100,000 inhabitants, the prevalence almost doubles than in those with 5,000 to 20,000 inhabitants: 6.4 per cent compared to 3.8 per cent. In municipalities with fewer than 5,000 inhabitants it is 4.3 per cent.