The original Wuhan virus, the causative organism of COVID 19 started its invasion in December 2019 and spread like wild fire internationally. The initial illness had a limited virulence with vulnerable groups like persons with high blood pressure, diabetes, immune comprised states and those with existing heart disease bearing the brunt of mortality. The initial measures were lockdowns of variable periods with general hygienic measures coupled with routine testing and staying home isolated if symptomatic. Anti-viral drugs and other adjuncts like chloroquine, ivermectin, azithromycin, remdesivir, tocilizumab played a very minor role in cases with mild or moderate infections. Steroids and anticoagulants saved many lives in severe cases with severe pneumonia. The virus however continued to increase its virulence as if to counter the measures taken against its spread and treatment strategies. It started mutating into alpha, beta, Kappa and delta variants.
The delta variant of SARS-Cov2 virus is the most talked about variant these days. it was first isolated in Maharashtra, India, and is the dominant strain in more than 170 countries worldwide, besides India, according to WHO. This variant B.1.617.2, according to a recent study is more than twice as contagious as the previous strains like the beta strain B.1.351. It has a higher replication and spike mediated entry meaning thereby greater potential of causing infection. In two different studies from Canada and Scotland, patients infected with the Delta variant were more likely to be hospitalized than patients infected with Alpha or the original virus that causes COVID-19. Even so, the vast majority of hospitalization and death caused by COVID-19 are in unvaccinated people. The greatest risk of transmission is among unvaccinated people who are much more likely to get infected, and therefore transmit the virus.
The protection provided by the vaccine after 2 doses or a previous COVID infection is less against this strain and breakthrough infections are common. However, the severity of infection and need for hospitalization is much lower in vaccinated individuals. The fully vaccinated people who get infected with the delta variant are capable of infecting others but for a shorter period of time.
Importance of getting vaccinated:
Vaccination against COVID with both the doses is pivotal for protection against getting a serious infection even with the delta strain. No vaccine produces 100% protection. The present data indicates that larger number of antibodies would be required to block this strain but the virulence of the infection is certainly reduced. This means that even though the risk of breakthrough infections is low, there will be thousands of fully vaccinated people who become infected and able to infect others, especially with the surging spread of the Delta variant. Low vaccination coverage in many communities is driving the current rapid surge in cases involving the Delta variant, which also increases the chances that even more concerning variants could emerge. High vaccination coverage will reduce spread of the virus and helps prevent new variants from emerging.
Vaccines also need to be upgraded as new strains emerge. The vaccination drive has really picked up in our country and hesitancy to take it is taking a back seat. We need to get data and guidelines for how long does the efficacy of vaccine last for after the 2nd dose. For persons who had their 2nd dose of the Astra Zenica, Covishield (the most frequently used vaccine in India) in February, it is already more than 6 months. In the US the immune compromised population is being given the booster dose. The need for a booster dose seems to be growing. With the availability of the vaccines in adequate quantity, it should be on the cards. Whether it should be the same vaccine or a different one also needs to be worked out?
What about children?
The infections in children have been in general been mild and not associated with serious consequences. Vaccinating this population is still a debatable issue. The US CDC recommends that everyone aged 12 years and older get vaccinated as soon as possible and the Pfizer and Moderna vaccines have proven safety in this population. Covishield vaccine has not been evaluated in this population. However, the India company Zydus Cadila has developed the world’s first DNA-plasmid vaccine for this age group. It has recently received emergency use authorization by the Drug Controller General of India for use in adolescents 12 years old and above. Although at present a 3-dose vaccine injected without a needle by a high-pressure nozzle, the recent studies have shown equivalent immunogenicity with a 2-dose vaccine. Its efficacy against delta strain is also a subject of study.
There is a classical case reported in May this year in Marin County, California, USA where an un vaccinated teacher who was infected and was taking classes without even wearing a mask infected 50% of the children in the classroom and the infection correlated with the proximity to the teacher. By the time teacher was tested positive the spread had already occurred. These children spread the infection and 27 adults reported symptoms and tested positive. On genome testing all those tested had delta variant as the causal agent.
Till now the guidance is that parents and school teachers all need to be vaccinated in order to keep children safe. However, with opening up of schools and more relaxations coming in a safe vaccine has an important place.
Tail piece:
Our current knowledge about the Delta variant, the current vaccine coverage in the community and some limitations of the current vaccines including the break through infections the preventive strategies continue to have a very important role. The role of mask wearing in public places and high-risk indoor situations to prevent spread of the pandemic continues to be as important as the administration of the vaccine. Combining the two strategies is the key as the waxing and waning pandemic of COVID-19 continues and new variants like the highly infectious Delta keep on emerging.
Prof Upendra Kaul Founder Director Gauri Kaul Foundation, Recipient of Dr B C Roy Award and Padma Shri
Disclaimer: The views and opinions expressed in this article are the personal opinions of the author.
The facts, analysis, assumptions and perspective appearing in the article do not reflect the views of GK.