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Mutations of the SARS-CoV-2 virus are characterized by mutations in certain amino acids of its spike protein, thus changing its structure, and by extension reducing the effectiveness of antibodies. The main characteristic of the Delta mutation (B.1.617.2) is its high transmissibility in a very short time of exposure, in all age groups, including children.

The emergence of the Delta mutation has changed the epidemiological data and threatens mainly the unvaccinated, thus causing a rapid increase in cases, especially in childhood and adolescence. A recent study published in the journal Nature studies the sensitivity of the Delta mutation to monoclonal antibodies approved for the treatment of COVID-19, to antibodies from sick patients and to antibodies after vaccination.

According to current data:

• The Delta mutation at the laboratory level appeared resistant to certain monoclonal antibodies.
• In sick patients, up to 12 months after symptoms, a reduction in antibody efficacy of up to 4 times was observed compared to the Alpha mutation (B.1.1.7).
• Sera from individuals who received only one dose of the Pfizer or AstraZeneca vaccines did not appear to be protective against the Delta mutation. On the contrary, two doses of these vaccines create sufficient protection in 95% of those vaccinated.
• The effectiveness of antibodies against the Delta mutation is reduced 3 to 5 times compared to the Alpha mutation.

According to the international organizations EMA, FDA, regarding the effectiveness of the four vaccines available in the E.U., all four are highly effective against the Delta mutation.

More specifically, the observational study of approximately 14,000 cases by Public Health England (PHE) showed that the Pfizer / BioNTech vaccine, and by extension Moderna, reach an efficacy rate against severe disease and the need for hospitalization of 96%, while AstraZeneca reaches 92% after administering both doses.

The single-dose vaccine from Johnson & Johnson reaches a protection rate of 85%.

According to Meaghan Kall, an epidemiologist at PHE, in the United Kingdom, where the Delta mutation dominates, but more than 50% of the population has been vaccinated, the rate of new deaths from the SARS-CoV-2 virus is 20 times lower compared to the highest rate recorded to date.

Recently, the FDA and EMA approved the Pfizer/BioNTech vaccine for children aged 12-15, while the EMA approved the Moderna vaccine for children aged 12-17. Clinical trials are being expanded to include children aged 5-11.

However, the question remains as to whether COVID-19 vaccines remain equally effective in preventing infection, transmission, and spread of the virus.

Observational studies in the United Kingdom so far have shown that two doses of the Pfizer vaccine were 88% effective against symptomatic disease from the Delta variant, while an observational study from Scotland showed an efficacy rate of 79%. Real-world efficacy data from the remaining vaccines are still awaited.

Moderna reported encouraging results from laboratory tests against the Delta mutation, as its vaccine shows a twofold reduction in neutralizing antibodies. Johnson & Johnson, on the other hand, reported that its vaccine offers “strong protection” against the disease.

Given the urgent need to accelerate the global effort to achieve immunity against COVID-19, these data indicate that there should be continuous vigilance regarding the Delta mutation, which is also spreading rapidly in our country.

Timely full vaccination, as well as the unremitting use of protective masks, can effectively contribute to addressing the situation. The most important priority of the international community should be to increase vaccination coverage worldwide.