5% of Spain's Population Estimated to Have COVID-19 Antibodies, Casting Doubt Over Herd Immunity: Study
Thu, April 22, 2021

5% of Spain's Population Estimated to Have COVID-19 Antibodies, Casting Doubt Over Herd Immunity: Study


The COVID-19 situation in Europe is getting worse as days go by. And for Spain, herd immunity is likely unachievable even if about 5% of its population developed antibodies against the disease.

The goal of herd immunity is being doubted by researchers from Spain. Their research revealed that an estimated 5% of the country's population developed antibodies against COVID-19. But the number of people with antibodies required to support herd immunity should be at least 70%. If lives were gambled to achieve that goal, more people would die from the disease, and healthcare systems might collapse. They published their findings in the journal The Lancet.

The COVID-19 Numbers in Europe and Spain

In the July 6, 2020, report by the World Health Organization of the United Nations, the total confirmed cases of COVID-19 in Europe were 2,791,160, while the total confirmed deaths were 200,238. Within 24 hours, 16,939 new cases and 357 new deaths were reported by countries in the region. Russia was found with the highest number of confirmed cases at 687,862, but the UK had the highest number of deaths at 44,220. Russia's cases were mainly classified as clusters of cases while UK's cases were classified as community transmission.

Meanwhile, Spain's efforts attempted to slow the spread of the disease, yet the country faced high numbers of confirmed cases and deaths. As of July 6, 2020, the country reported 250,545 confirmed cases and 28,385 confirmed deaths. In the last 24 hours, no new case or death was reported – a rare event in a severely affected country. Still, the numbers in Spain were classified as clusters of cases. This indicated that increasing efforts in containing COVID-19 could effectively prevent case surges in the future.

Other countries with more than 100,000 confirmed cases include Italy at 241,611, Turkey at 205,758, Germany at 196,554, and France at 158,734.



Researchers Cast Doubt Over Herd Immunity

Dr. Gregory Poland, Director of the Vaccine Research Group at the Mayo Clinic, discussed the herd immunity in COVID-19 back in June 2020. The role of herd immunity remains essential in protecting people from the disease. But it can only be achieved if the main requirement is accomplished. This is one method of controlling the spread of the disease until a vaccine or specific treatment is developed. Though, pushing for herd immunity is not an easy objective because lives will be at stake.

Dr. Poland explained that herd immunity was accomplished after the Spanish flu pandemic ended. People who survived the 1918 pandemic resisted the 2009-2010 flu season due to the similarities in the two viruses. Both events involved strains of the H1N1 subtype of influenza A. Survivors of the Spanish flu were unaffected by the 2009-2010 swine flu that lasted for more than a year. The reason why they resisted the latter disease has been the antibodies they develop from the Spanish flu. And in communities where they lived, their presence restricted the movement of the swine flu.

Unfortunately, those veterans were likely clustered in select territories. Their acquired immunity could only protect a limited number of communities from the swine flu. If more people inherited the antibodies for Spanish flu, the latter disease would have not infected more people than it should. So, if compared to COVID-19, lots of people would need to get sick and recover to protect others. The definition of lots of people would mean 70% of a country's outstanding population. In the US, 70% of the population would be equivalent to more than 200 million individuals – all survivors of COVID-19.

In The Lancet, Spanish researchers showed that herd immunity, at this time, would be an impossible feat for COVID-19. Their findings strongly recommend the current preventive measures to control the spread of the disease. Those measures were likely to reduce new cases and deaths, compared to the application of herd immunity. Their support for preventive measures was due to the small number of people who developed antibodies against the novel illness.



"The majority of the Spanish population is seronegative to SARS-CoV-2 infection, even in hotspot areas. Most PCR-confirmed cases have detectable antibodies, but a substantial proportion of people with symptoms compatible with COVID-19 did not have a PCR test and at least a third of infections determined by serology were asymptomatic. These results emphasize the need for maintaining public health measures to avoid a new epidemic wave," researchers wrote.

In the study, a total of 35,883 households were selected in Spain using two-stage random sampling, which examined municipality and provincial size. The selection yielded 61,075 participants or 75.1% of all households contacted. Participants answered a questionnaire from April 27 to May 11, 2020, to report their history of symptoms related to COVID-19. The questionnaire also included risk factors, point-of-care antibody tests, and blood samples for immunoassay tests.

Results revealed that 5% of the participants had tested positive in the point-of-care test, while 4.6% tested positive for immunoassay. The range of specificity and sensitivity from test results was between 3.7%, indicating positive in both tests, and 6.2%, indicating positive from either test. Among participants, 7,273 exhibited at least three symptoms of associated with COVID-19, but one-third or 33.33% were asymptomatic. Only 19.5% of symptomatic participants, who tested positive in both tests, reported a previous test involving PCR.

By geography, researchers detected a disparity in the prevalence of cases based on positive test results. More than 10% of positive tests were tracked down around Madrid, and less than 3% were traced back to coastal areas. The disparity supported the number of confirmed cases in Spain, wherein the prevalence was definitely high in cities with widespread outbreaks but low in areas without notable outbreaks.

If scaled countrywide, 5% of participants who tested positive in the point-of-care or antibody test represented 5% of the country's population with antibodies for COVID-19. Despite the impact of the pandemic, Spain must fulfill the remaining 65% requirement to achieve herd immunity. That would be more cases and deaths, which the country could no longer handle.

Because herd immunity for COVID-19 is a dangerous game to play, experts prefer social distancing, proper handwashing, face mask, and other preventive measures as weapons against the disease. Previous studies showed that more people are likely unexposed to the disease, compared to the number of people exposed. So, inducing herd immunity through natural infection may lead to catastrophic outcomes.