通过大部分人口产生免疫力来阻断病毒传播的群体免疫策略，在西方国家中一直被寄予厚望。日前，西班牙的一项大规模研究得出结果称，从西班牙人口产生新冠病毒抗体的比例来看，群体免疫恐怕难以实现。A woman wearing a protective face mask walks past a closed souvenirs store, amid the coronavirus disease (COVID-19) outbreak, in Madrid, Spain, July 8, 2020. REUTERS/Susana Vera
Covid-19 antibodies in Spain’s population “are insufficient to provide herd immunity,” a new study has claimed, despite the country being one of the worst-affected by the pandemic.
In a peer-reviewed paper published in the Lancet medical journal Monday, researchers from Harvard, MIT and several Spanish institutions analyzed findings from a widescale study on antibody prevalence in Spain.
More than 251,700 cases of coronavirus have been confirmed in Spain, while the virus has killed 28,388 people in the country to date, according to data compiled by Johns Hopkins University. With 607 deaths per million people, Spain has the third-highest number of deaths relative to population in the world, according to Our World in Data.
Households all over Spain were invited at random by the research team to take part in the study, which aimed to determine the proportion of the population that had developed antibodies for the coronavirus.
A total of 61,075 people agreed to participate in the study, which was carried out between April 27 and May 11. Participants answered a questionnaire on coronavirus symptoms, were given a point-of-care finger prick test, and had the option to donate blood for further laboratory testing (which 51,958 of the people in the study did).
point-of-care:即时的A woman adjusts her face mask as she walks out of a store advertising going-out-of-business sales, amid the coronavirus disease (COVID-19) outbreak, in Madrid, Spain, July 8, 2020. REUTERS/Susana Vera
Just 5% of participants presented with antibodies from point-of-care tests, while antibodies were detected in 4.6% of the blood samples.
According to the findings, there was “substantial geographical variability,” with antibodies found in 10% of samples from Madrid but just 3% of those taken from coastal areas.
Around a third of those who tested positive for Covid-19 antibodies had been asymptomatic while infected with the virus, the study found.
Among those who reported having been unwell with symptoms of Covid-19 prior to the study, 16.9% tested positive for antibodies. Meanwhile, 90% of those who had tested positive for the coronavirus more than 14 days before taking part in the study had antibodies detected in their lab-tested blood samples.
"Despite the high impact of Covid-19 in Spain, prevalence estimates remain low and are clearly insufficient to provide herd immunity,” the report’s authors said. “This cannot be achieved without accepting the collateral damage of many deaths in the susceptible population and overburdening of health systems. In this situation, social distance measures and efforts to identify and isolate new cases and their contacts are imperative for future epidemic control.”
该报告的作者称：“尽管新冠病毒对西班牙造成了很大冲击，但是抗体的普及率依然偏低，显然不足以产生群体免疫。要达成群体免疫，就不得不接受易感人群大量死亡和让医疗系统超负荷的附带损害。在这种情况下，未来的疫情防控中必须实行社交隔离措施，努力发现和隔离新病例及其密切接触者。”A man wearing a protective feace mask stands during the lockdown amid the spread of the coronavirus disease (COVID-19) in Burela, Spain July 6, 2020. REUTERS/Miguel Vidal
Herd immunity is achieved when immunity is built among the general population through some exposure to a virus or infection. The strategy has been cited by health officials in Sweden, which controversially did not impose a lockdown.
However, many experts are skeptical about the effectiveness of such an approach, warning that immunity to the coronavirus is not guaranteed after infection or may only last a short while.
Speaking on CNBC’s “Squawk Box Europe” on Monday, Danny Altmann, professor of immunology at Imperial College London, said it was not a “safe bet” to rely on immunity to Covid-19 as a strategy for coping with the pandemic, adding that herd immunity strategies were “probably never going to work.”
Depending on how contagious an infection is, between 50% and 90% of a population must be immune to achieve herd immunity, according to experts at Johns Hopkins University, who estimate that at least 70% of the population would need to be immune to Covid-19 for herd immunity to be realized.
Top White House health advisor Dr. Anthony Fauci speculated last month that if Covid-19 behaved like other coronaviruses, there “likely isn’t going to be a long duration of immunity” from antibodies. Meanwhile, the WHO has stated that it remains unclear whether those who have already caught the virus once will be immune to getting it again.