WHO has made it very clear that the Delta variant of the COVID-19 virus is a variant of concern because it has increased transmissibility. The Delta variant has been reported in 96 countries and there are a number of factors contributing to increased transmission globally.

Explaining why the world is seeing such a rapid increase in the spread of the Delta variant, WHO’s Dr Maria Van Kerkhove told Science in 5, “We have increased social mixing and increased social mobility, which increases the number of contacts that individuals have. The relaxation or the inappropriate use of public health and social measures. Proven public health and social measures that we know prevent infections, reduce the spread of somebody who is infected with the virus to others and save lives. Another factor is the uneven and inequitable distribution of vaccines.”

It is abundantly clear that the world remains largely susceptible to infection, including any variants of concern, including the Delta variant.

What are the key things about the Delta variant?

The Delta variant, which is said to be a highly contagious and severe form of the SARS-CoV-2 virus strain, was first identified in India in December. The country faced a deadly second wave because of the Delta variant. Great Britain also bore brunt of it and it is now the dominant strain in the US.

• More contagious than the other virus strains: The World Health Organisation (WHO) called the Delta variant of the SARS-CoV-2 virus “the fastest and fittest.” The US CDC called Delta “a variant of concern”.
• Why unvaccinated people are more at risk: People who are not fully vaccinated against COVID-19 yet are already at risk and even more so from the Delta variant. In India, people below the age of 18 years are not eligible for COVID-19 vaccines yet and not all adults have been vaccinated so far due to the sheer size of the population, vaccine hesitations and vaccine shortage.

Fear of ‘hyperlocal outbreaks’: Epidemiologist F Perry Wilson told Yale Medicine that if residents of a certain locality are not vaccinated enough there is a high possibility of the Delta variant spreading very rapidly with hardly any shield to firewall the virus.

• No alternative to vaccination: Although vaccines are still getting upgraded as new knowledge of the SARS-CoV-2 virus emerges every other day, the Pfizer-BioNTech vaccine is said to have 88 percent effectiveness against symptomatic disease and 96 percent effectiveness against hospitalisation from Delta. The Oxford-AstraZeneca is 60 percent effective against symptomatic disease and provides a 93 percent chance against hospitalisation. Both Moderna and Johnson & Johnson have claimed to have some amount of effectiveness against the Delta variant. In the US, virtually all recent Covid hospitalisations and deaths were occurring among unvaccinated people.

Why vaccinated people can also transmit the Delta variant of infected

On 4 July, Dr Anthony Fauci had told NBC that “it’s feasible that a fully vaccinated person can be an asymptomatic carrier of COVID, and potentially transmit the virus, including the more contagious delta variant”. The only silver lining is perhaps that Fauci said vaccinated people who get infected have significantly less viral load in their nasopharynx.

On Monday, repeating a similar observation, Dr Soumya Swaminathan, the WHO chief scientist, said, “There are reports coming in that vaccinated populations have cases of infection, particularly with the Delta variant. The majority of these are mild or asymptomatic infections.”

However, hospitalisations are rising in some parts of the world, mostly where vaccination rates are low and the highly contagious delta variant is spreading, Swaminathan said.

“The Delta variant is ripping around the world at a scorching pace, driving a new spike in cases and death. Not everywhere is taking the same hit, though,” WHO Director-General Tedros Adhanom Ghebreyesus said. “We are in the midst of a growing two-track pandemic where the haves and have-nots within and between countries are increasingly divergent in places with high vaccination coverage.”

Why masking and social distancing is unavoidable

The WHO chief scientist said that the organisation is urging people to continue wearing masks and practice social distancing because it “certainly reduces your chances of severe hospitalisation and death significantly”. Some studies say that those infected with COVID-19 after vaccination produce much less virus than those who are unvaccinated.