Delta variant can spur surge in COVID-19 cases worldwide; five things we know about the VoC


The Delta variant, also known as B.1.617.2, can spread more easily, according to the US Centre for Disease Control

The highly transmissible Delta variant, first detected in India, is sweeping across the world as countries race to inoculate their populations to ward off fresh outbreaks and allow economies and daily life to resume.

News headlines from this week ranged from reporting an uptick in US cases after months of decline to infections skyrocketing by over 500 percent in the Netherlands. Meanwhile, leaders who opened up their countries too early, or those who disregarded the importance of masks had to eat their words.

If the irrefutable scientific evidence and pandemic data from around the world was insufficient, then the World Health Organisation on Wednesday also spelled out the threat in as many words: Its director said that the increased transmissibility associated with the Delta variant is likely to result in substantial increases in case incidence and greater pressure on healthcare systems, particularly in contexts of low vaccine coverage.

From what we know so far, people who are fully vaccinated against the coronavirus appear to have protection against Delta, but jury is still out on whether or not vaccination alone will suffice in face of the new variant.

The problem is further compounded by the overload of information and the constantly evolving research that renders past information redundant very quickly. But we tried to compile five facts that scientists are fairly certain of and are being used to dictate policy decisions.

1) It is more contagious

The Delta variant, also known as B.1.617.2, can spread more easily, according to the US Centre for Disease Control. The strain carries the genetic code from two other mutations, E484Q and L452R, which helps it to break into the human immune system and invade the organs.

In fact, researchers have said that the Delta variant is about 50 percent more contagious than the Alpha variant, first identified in UK, which was already 50 percent more contagious than the original coronavirus first identified in China in 2019.

“In a completely unmitigated environment, where no one is vaccinated or wearing masks, it is estimated that the average person infected with the original coronavirus strain will infect 2.5 other people. In the same environment, Delta would spread from one person to maybe 3.5 or 4 other people,” says Dr F Perry Wilson of Yale School of Medicine.

2) Fewer antibodies… 

Several lab tests show that the Delta variant seems to have stronger resistance to vaccines than other variants do.

A British study published in The Lancet medical journal in early June looked at levels of neutralising antibodies produced in vaccinated people exposed to the Delta, Alpha (first identified in Britain) and Beta (first identified in South Africa) variants.

It found that antibody levels in people with two doses of the Pfizer/BioNTech shot were six times lower in the presence of the Delta variant than in the presence of the original COVID-19 strain on which the vaccine was based.

A French study from the Pasteur Institute concluded that neutralising antibodies produced by vaccination with the Pfizer/BioNTech jab are three to six times less effective against the Delta variant than against the Alpha variant. The same study found that the levels of neutralising antibodies produced against the Delta variant were “almost undetectable”after a single shot of Pfizer and AstraZeneca vaccines, both of which are two-dose regimens.

3) … but vaccines still work

Although they represent an essential marker, the levels of antibodies measured in a lab are not enough to determine the efficacy of a vaccine.

In particular they do not take into account a second immune response in the form of killer T cells: which attack already-infected cells and not the virus itself. As a result, real-world observations are crucial to measuring vaccine effectiveness, and the first results are reassuring.

Data published by Public Health England suggested that the Pfizer-BioNTech vaccine was 88 percent effective against symptomatic disease from the Delta variant two weeks after the second dose, compared to 93 percent effectiveness against the Alpha variant.

Two doses of the Pfizer/BioNTech jab prevent 96 percent of hospitalisations due to the Delta variant, while AstraZeneca prevents 92 percent, according to a study involving 14,000 people.

4) Disease progression might be more severe

While more research is needed, early information about the severity of Delta includes a study from Scotland that showed the Delta variant was about twice as likely as Alpha to result in hospitalisation in unvaccinated individuals (and vaccines reduced that risk significantly).

5) Could exhibit different symptoms

According to an article The New York Timesdoctors from Southeast China are reporting that patients are becoming sicker and their conditions deteriorating more quickly than the patients they treated at the start of the pandemic. India’s experience has been similar with people reporting symptoms ranging from diarrhoea to headaches, while the tell-all symptom of loss of smell and taste was no longer held to be the benchmark differentiator between common flu and COVID-19 .

Another article published on Gavi vaccine alliance’s website noted that another study from UK also suggested that the symptoms associated with COVID-19 may be changing. Since the start of May, the number one symptom reported by app users with a confirmed infection has been headache, followed by sore throat, a runny nose, and fever. “Cough is rarer and we don’t even see loss of smell coming up in the top ten anymore,” said Prof Tim Spector, who is leading the study.

So is delta variant a bigger problem than early stages of pandemic?


The increased transmissibility associated with the Delta variant along with decreasing caution and COVID-19 appropriate behaviour means that it is likely to become the dominant variant globally over the coming months

Moreover, in large parts of the world, there remain gaps in epidemiological surveillance, testing and genomic sequencing, and this limits our ability to monitor and assess the impact of current and future variants in a timely manner.

The global number of new cases reported last week (July 5-11, 2021) was nearly 3 million, a 10 percent increase as compared to the previous week. Following a steady decline for nine consecutive weeks, the number of weekly deaths increased by 3 percent this week compared to the previous week, with over 55,000 deaths reported, a WHO update said.

Globally, COVID-19 incidence increased with an average of over 4,00,000 cases reported each day as compared to 3,70,000 from the previous week.

The cumulative number of cases reported globally is now over 186 million and the number of deaths exceeds 4 million.

With inputs from agencies

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