Beating Delta and why we need all the vaccines we can get

Published September 28, 2021, 12:12 AM

by Dr. Edsel Salvana

(Not just the Western ones)

CLINICAL MATTERS

Dr. Edsel Maurice T. Salvana

Despite record numbers of cases across the world as a result of the Delta variant rampage, death rates from COVID-19 in countries with high vaccination rates have been dropping dramatically. Along with decreasing death rates are fewer severe cases requiring hospitalization. Among breakthrough cases in those who are fully vaccinated, most infections are asymptomatic or mild. In the UK, where cases have recently increased to almost the same number of cases at its peak in January 2021, the fatality rate has remained at about 200 deaths a day compared to over 1,500 deaths a day last January. This phenomenon is termed “decoupling,” which refers to the fact that deaths no longer rise proportional to the number of cases. Since the current dominant variant Delta is at least as deadly as the previous variants of concern, the most likely factor for this decrease in deaths is widespread vaccination. Looking at countries with low vaccination rates, the “decoupling” phenomenon is noticeably absent, with countries like Indonesia and India reaching record highs of deaths of more than 1,000 deaths per day and 4,000 deaths per day respectively at the height of their Delta spikes.

Due to the two to three-fold higher transmissibility of Delta, the number of cases in a country is expected to increase exponentially as Delta enters and becomes the dominant variant. While it is unclear if Delta is more deadly than the other COVID-19 variants, it is known to be at least as deadly as the other variants of concern. Therefore, the level of deaths should remain proportional to the number of cases compared to previous case spikes. In the Philippines, a nearly threefold increase in cases driven by Delta in August and September 2021 compared with the spike in March and April 2021 driven by Alpha and Beta should have resulted in a similar threefold increase in deaths. Instead, the daily deaths in August 2021 peaked to just above the highest numbers for April 2021 and are now paradoxically going down. The most likely reason is that increasing vaccination rates are decreasing the number of severe cases that result deaths, especially for the vulnerable population.

The most impressive numbers on vaccination come from the A1 priority group for vaccination, or the healthcare workers. With over 95 percent fully vaccinated, healthcare workers have gone from one of the populations with the highest fatality rates to one of the lowest. Current COVID-19 case fatality rates for healthcare workers are below the average of the general population. For A2 (elderly) and A3 (comorbid conditions) vulnerable groups, significant decreases in fatality rates have also been seen. Given the lower vaccination coverage for these populations compared with A1, however, the drop has not been as dramatic.  

In the National Capital Region, the early lockdown between Aug. 6 and Aug. 20, 2021 significantly tempered the number of active cases despite the entry of Delta. A previous column (https://mb.com.ph/2021/09/07/our-lockdowns-are-worth-it-but-how-do-we-move-forward/) noted that the initial projected active cases in NCR for Aug. 31 at its most conservative was 66,403 cases, but the active cases on the actual date was 40,157 cases.

As we near Sept. 30, 2021, revisiting those same models shows that the projected estimate of active cases in NCR by Sept. 30, 2021 was 152,776 at its most conservative to up to 269,694 active cases. These numbers are not inconceivable, as the number of daily cases in India reached more than 400,000 COVID-19 cases per day at the height of their Delta wave.

As of this writing (Sept. 23, 2021), the number of active cases in NCR is 41,609. This is over 110,000 active cases lower than anticipated. This incredible result is not just from the preemptive lockdown but is also due to the enhanced vaccination program, which has already full inoculated over half of eligible population in NCR, as well as augmented PDITR (Prevent-Detect-Isolate-Treat-Reintegrate) strategies implemented by the MMDA and NCR LGUs.

It is therefore distressing that disinformation on the efficacy of specific vaccine brands continues to cause vaccine hesitancy. A report by the Philippine FDA on Aug. 29, 2021 showed that out of more than 13.87 million fully vaccinated individuals, only 242 individuals had breakthrough infection resulting in five deaths. That’s a tiny 0.0017 percent breakthrough and an even lower number of breakthrough fatalities. Nearly half of the vaccines used at the time of this analysis were Sinovac at 6.8 million fully vaccinated. This is followed by Janssen (3.6 million), Astra (2 million), and Pfizer (1.2 million). This highlights the excellent efficacy of all the vaccines used locally.

We all need to combat vaccine hesitancy from misinformation. Increasing breakthrough infections are due to the nature of Delta. It is not from waning immunity, as virtually no one in the country has been fully vaccinated beyond six months. Protection from severe disease remains robust for all COVID-19 vaccines. Protection from clinical disease has been affected by the variants of concern.

The “low” clinical efficacy (protection against developing COVID symptoms) initially ascribed to the Sinovac trial in Brazil was a result of the predominant Gamma variant of concern circulating at the time of the study. We know that, similar to Delta, Gamma has decreased susceptibility to COVID-19 vaccines in general. Despite this, however, Sinovac still protected very well against hospitalization and deaths. Data from countries like Turkey prior to the entry of Delta showed that Sinovac in Phase 3 trials had an over 80 percent vaccine efficacy against clinical disease. This is just as good as, if not better than Janssen and Astra, and it protected against almost all hospitalizations. On the other hand, clinical efficacy for the Pfizer vaccine has gone down to 30 to 40 percent against Delta in Israel, but the vaccine continues to protect against severe disease at a very high level. Recent data on the performance of Sinovac and other inactivated vaccines against Delta from a recent outbreak in China showed full protection against severe disease.

These findings imply that all our vaccines are at the same level right now against Delta as the main variant, i.e., decreased protection from clinical disease but continuing very high protection against severe disease.

Therefore, there is no scientifically defensible rationale for choosing one vaccine brand over another. The objective is to vaccinate and protect as many Filipinos as possible against severe disease. When reformulated vaccines arrive, we may be able to restore clinical efficacy against the variants of concern. Until then, all COVID-19 vaccines work well and will save lives. Get the one that is offered to you. Being conscious about the brand just prolongs the pandemic and puts your own life at risk.

 
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