The COVID-19 pandemic continues its rampage throughout the world with 11.4 million cases and 540,000 deaths. The WHO estimates that 4.5% of confirmed cases will die and approximately 20% will require oxygen supplementation for low PaO2.
Herd immunity. When a high proportion of a population are immune to a disease through vaccination or catching the disease naturally, the disease can no longer spread and the “herd” is immune and hence protected. For measles, which is highly infectious it is about 95%. For COVID it is unknown, probably at least 70%, but a better guess is 80-90%.
Today the Lancet has published an interesting study from Spain of Corona virus antibody levels. A community sample of 60,000 underwent serology testing. Spain has had 249,000 confirmed cases and more than 28,000 deaths (July 2) and yet had a low level of antibodies in the community (5% nationwide and 10% in a Madrid hotspot)1.
In a commentary on the article Eckerle and Meyer point out that there have been similar findings of low antibody levels in post-peak studies in Wuhan and Switzerland. These levels are well below the levles required to achieve herd immunity (probably 80-90%)2.
“In light of these findings, any proposed approach to achieve herd immunity through natural infection is not only highly unethical, but also unachievable. With a large majority of the population being infection naive, virus circulation can quickly return to early pandemic dimensions in a second wave once measures are lifted2.”
Achieving a COVID-19 Vaccine.
To date little objective information on progress is available. Most information comes from press releases more designed to boost stock prices than to impart scientific knowledge. However the New England Journal of Medicine has published a very informative review of the vaccine development process and the ways it is hoped to speed this up3. Progress is likely to be slow and it probably be some years before effective vaccines are widely available.
All of these articles are available for free download at the journals home pages.
- Pollán M, Pérez-Gómez B, Pastor-Barriuso R, et al. Prevalence of SARS-CoV-2 in Spain: a nationwide, population-based seroepidemiological study Lancet 2020.
- Eckerle V, Meyer B. SARS-CoV-2 seroprevalence in COVID-19 hotspots. Lancet 2020
- Deming M, Michael N, Merlin Robb M, Cohen M, Neuzil K. Accelerating Development of SARS-CoV-2 Vaccines — The Role for Controlled Human Infection Models. NEJM 2020.
Colin Binns, MBBS, PhD
Editor-in-Chief, Asia-Pacific Journal of Public Health
School of Public Health, Curtin University, Perth, Australia
Wah Yun Low, PhD
Managing Editor, Asia-Pacific Journal of Public Health
President, Asia-Pacific Academic Consortium for Public Health
Deputy Executive Director, Asia Europe Institute
University of Malaya, Kuala Lumpur, Malaysia
Victor Hoe Chee Wai, MBBS, PhD
Webmaster, Asia-Pacific Academic Consortium for Public Health
Department of Social and Preventive Medicine, Faculty of Medicine
University of Malaya, Kuala Lumpur, Malaysia
