Delta Variant pushes up ‘herd immunity’ threshold closer to 90%, medical experts say


The Delta Coronavirus Variant, a mutated form of the COVID-19 virus that is two times more transmissible, has raised the ‘herd immunity’ threshold from 70 to around 90 percent, medical experts advised recently.

“The problem here is that the Delta Variant is twice as more transmissible than the original virus,” Professor Dr. Ricardo Franco, a member of the Infectious Diseases Society of America (IDSA), said during a Tuesday, August 3rd, media briefing.


“That pushes the overall population immunity thresholds much higher. The original SARS-Cov-2 comes within the range of herd immunity thresholds around 60 – 70 percent. For Delta, those threshold estimates go well over 80 percent; maybe approaching 90 percent.”



The IDSA’s estimation is consistent with findings from a study published last month in the International Journal of Environmental Research and Publish Health, entitled “Projecting the Impact of SARS-CoV-2 Variants and the Vaccination Program on the Fourth Wave of the COVID-19 Pandemic in South Korea.” Therein, author Eunha Shim (July 2021) concluded:


“Our study unequivocally suggests a substantial impact of vaccination program on mitigating the severity of COVID-19 infection at the population level. … However, this strategy is unlikely to help achieve herd immunity with the potential emergence of more contagious SARS-CoV-2 variants, as the current pace of vaccine rollout is insufficient to prevent the exacerbation of cases, hospitalizations, and deaths expected.”


As of August, The World Health Organization (WHO) has reported that more than 100 countries have confirmed cases of the Delta Variant. While the Delta Variant is suspected to be present in Belize, the Ministry of Health and Wellness (MOHW) is awaiting verification from Baylor College, as the country does not currently possess the ability to conduct the necessary tests to identify the specific version of the virus locally.



MOHW’s vaccination report for August 6th shows 33% of Belizeans are vaccinated.

Nevertheless, whether it is the Alpha, Delta, or any other variant listed on the WHO’s list of variants of concern, the medical experts concur that the role of the vaccine remains paramount. Dr. Franco explained, “The key here is that the overwhelming majority of infections are occurring among the unvaccinated.”





As of August 6th, the MOHW has reported that 139,413 Belizeans have received at least one dose of the COVID-19 vaccine. Based on the Statistical Institute of Belize (SIB)’s 2020 population data, this figure represent about 33 percent of the total population and approximately 58 to 60 percent of the country’s adult population. The Ministry also reported that 55,143 Belizeans (or 13% of the whole population and 23% of adults) are fully vaccinated. Herd immunity is defined the threshold beyond which the larger population is protected from the virus due to vaccination or natural immunity gained from previous infection.



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