The Covid-19 pandemic is still raging, no doubt about it. However, just like any virus, health officials have already determined that the SARS-CoV-2 virus will definitely mutate to other strains or variants that may be highly transmissible, or deadlier—or even both, which is scarier.
Some of these variants initially bore names based on their country of origin but then the World Health Organization (WHO) decided to change them to protect the sensibilities of these countries when it comes to associating their country’s name to a deadly virus.
Hence, these variants were given names based on letters of the Greek alphabet, the more popular ones are the Alpha, Beta, Gamma and most recently, the B.1.617.2 or Delta variant, which was first identified by scientists in December 2020 in India.
So. what is the Delta variant? How is it different from the others in terms of symptoms, mode of transmission? Why does it affect more of the younger population? In short, is it more serious than the others? Should we all be scared, even those who have completed their jabs already?
Dr. Franco Felizarta, Infectious Disease and Internal Medicine Specialist. UP Medical Alumni Society in America (UPMASA), recently talked about this newest variant, even vaccine efficacy and effectiveness, during the latest webinar of The University of the Philippines, in partnership with UP Manila NIH National Telehealth Center and in cooperation with UP Philippine General Hospital entitled “The Delta Variant: What Every Frontliner Needs to Know.”
Knowing the variants
The Alpha variant which supposedly came from the UK is 50 percent more transmissible than the original virus from Wuhan, China but this Delta variant is 50 percent more transmissible than the Alpha variant. The Beta variant from South Africa has the same transmissibility as Alpha, while Gamma from Brazil has a higher transmissibility than Alpha but less than Delta. This effectively means that Delta is tops because it has the highest transmissibility.
“Disease severity has not really increased among the variants except for Gamma. In Manaus, Brazil, they thought they already had herd immunity and they had a bad second wave. There was also not much impact when it comes to diagnostics,” Dr. Felizarta said.
He pointed out that the Alpha is still No.1 in terms of global coverage, being present in 173 countries. “However, the Delta variant is fast catching up as it is now present in 104 countries already.”
Real-world vaccine effectiveness
Considered as mankind’s line of defense against the virus are the vaccines. How are they performing?
With regard to the AstraZeneca vaccine in fighting the Alpha and Delta variants, Dr. Felizarta said it was quite low for the symptomatic at 66 percent for Alpha and 60 percent for Delta, but for prevention of hospitalization, it’s a high 86 percent for Alpha and 92 percent for Delta, which is pretty good. “Even with one dose of AstraZeneca, it already prevents 76 percent of hospitalization for Alpha and 71 percent for Delta.”
As for the CoronaVac vaccine of Sinovac’s efficacy and effectiveness, it may not be too impressive for Covid-19 symptomatic patients but for the prevention of hospitalization and severe disease, Dr. Felizarta saw that it’s quite impressive, from 85-100 percent, especially in Chile which uses Sinovac. “Based on 10.5 million, they have the Alpha and the Gamma variants, and yet they still achieved 85 percent.”
For vaccine neutralization versus the variants, according to the Covid-19 Weekly Epidemiological Update by the WHO last July 6, 2021, CoronaVac even did better than AstraZeneca, and AstraZeneca did better against the other vaccines in terms of neutralization.
Vaccine breakthrough infection
Dr. Felizarta said that the higher the reproduction number, the higher the percentage needed to achieve herd immunity. For the Delta variant, which has high transmissibility, vaccination should have to be around 86 percent of the population.
“Remember that the higher the number of vaccinations the more difficult It becomes for the virus to be transmitted to unvaccinated community,” Dr. Felizarta pointed out.
But what happens if there is a vaccine breakthrough infection, defined by the US CDC as the infection of a fully vaccinated individual? The viral load is decreased by 40 percent, the fever symptoms is 25 percent versus 63 percent in the unvaccinated, and in terms of days spent in bed, only 1.5 days compared to almost four days for the unvaccinated so it’s milder compared to the unvaccinated, Dr. Felizarta explained.
In terms of household transmission, he said that the secondary attack for the unvaccinated is 10 percent, but if vaccinated with either AstraZeneca or Pfizer, it’s only 6 percent. “That’s almost a 50-percent decrease in household transmission in terms of breakthrough infection for unvaccinated versus the vaccinated.”
There is also decreased mutations in breakthrough infection, he said, which means the higher the vaccination rate, the lower the diversity.
“In summary, you have great protection against severe disease, including hospitalization and deaths among all vaccines against all variants and if there’s a breakthrough infection, it would be milder, the household transmission is lower and there is decreased mutations compared to the unvaccinated.”