Racing to herd immunity

Here are new real-world studies, this time from the United Kingdom (UK), which provides us with more information on COVID-19 vaccine efficacy. Unfortunately, the UK did not use Sinovac, which is the brand that is currently the most available in the Philippines.

The COVID-19 vaccines used in the study were by Pfizer/BioNTech and AstraZeneca/Oxford. The results, reported in www.cidrap.umn.edu, however offer us some useful insights.

The UK now has over half of its 68 million population partially vaccinated, and since the nationwide vaccine rollout that started in December, daily reported cases in April have significantly dropped to an average of below 5,000 cases (from a high of 69,000), and reported deaths to an average below 50 (from a high of 1,823).

The studies highlight the observed efficacy not only between the two vaccine brands, but also between one and two doses. Here are relevant results from the three studies separately conducted by the Public Health England Colindale in London, the Hull Teaching Hospitals in England, and the University of Edinburgh.

In the Colindale study, the authors wrote that the vaccines appeared generally effective, but not 100 percent against preventing infection. Thus, they advised health workers to continue observing recommended protective measures, including regular asymptomatic testing until this pandemic blows over.

Herd immunity

The more important observation, however, comes from a commentary by two doctors – Eyal Leshem, MD, of Chaim Sheba Medical Center in Israel, and Benjamin Lopman, PhD, of Emory University – on the study results that could further help public health officials and policy makers refine vaccination targets to achieve herd immunity.

Based on the findings of the Colindale results, the two doctors wrote that “nearly 100 percent of the population would need to be vaccinated with one dose or about 80 percent with two doses” to achieve herd immunity. Thus, “a one-dose strategy might be best for averting the most deaths, but higher population immunity to quell transmission will require a full course of two doses.”

In the Hull study, collated data showed that both symptomatic and asymptomatic COVID-19 infections dropped as vaccinations rose to 82.5 percent of hospital staff by Feb. 22. Specifically, the “single-dose (Pfizer vaccine) has been associated with a significant decrease in positive (COVID-19 tests) in both symptomatic and asymptomatic (healthcare workers), with the most dramatic effect on symptomatic illness.”

Edinburg study

A more comprehensive study can be gleaned from the Edinburgh data where the health documents of 5.4 million or 99 percent of the Scottish population were available and factored in during the early period when the vaccines were first administered.

Significantly, of the 1.3 million with an average age of 65 vaccinated against COVID-19, only 723 became ill of the infectious virus compared to 7,854 who did not receive the vaccine. A 91 percent effectiveness after the first Pfizer dose compared to 88 percent of AstraZeneca, resulting in reduced hospitalizations 28 to 34 days later.

For those 80 years and older, both vaccines showed an almost even effectiveness of 83 percent. Hospitalizations for this elderly group likewise dropped the most.

The Edinburg study is significant also in taking into account socio-economic status, residence in non-urban areas, and the presence of co-morbidities. For this reason, scientists are watching closely further data from reports on vaccinations administered to the rest of the population.

So far, 2.8 million or 61 percent of Scotland’s adult population have received the jab, while over one million or 23.5 percent have completed their required doses. Even with the addition of the Moderna vaccines, Scotland had to extend second dosage jabs to a 12-month interval due to supply shortages.

Surplus vaccines

Rich countries like Israel, the US, and the United Arab Emirates lead the world in terms of vaccination efforts, and as they go through the time frame of having their citizens complete full doses, new data is emerging about these countries having more than enough of what their entire populations need.

Countries awash in vaccine supplies include Canada (435 percent of population covered), the UK (364), New Zealand (329), Australia (286), the EU nations (235), and the US (200). In contrast, developing countries have barely been able to secure enough for even half their population.

The Philippines has, to date, secured vaccines already for 45 percent of the population, definitely not yet enough to vaccinate the desired 70 to 80 percent of the nation by yearend. The rollout is even slower, with only 1.65 million or 1.5 percent of the population getting two shots or less.

It would be best for the Philippines to seize the opportunity that these excess vaccine stocks represent to increase its stockpile levels, especially since our government has repeatedly said that there is money to purchase the needed vaccines. Let’s hope that this does not entail getting into more vaccine diplomacy deals.

Countries with large populations like China, South Korea, and Vietnam – which have managed to keep infection levels low despite a slow vaccination program, attribute their success to effective controls centered on contact tracing with support from the usual health protocols like mask wearing and social distancing.

We know now that our government has a poor capability for keeping infection levels at manageable levels, and more than one year under quarantine for large parts of the country is proof of this.

Our only hope now to get the economy back on track is to acquire herd immunity through vaccinations at the quickest time before any new variants resistant to the current vaccines surface. That’s going to be a tall order given that we need to jab 350,000 Filipinos every day to catch up.

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