As newly emerging, most contagious, variants of the COVID-19 causing coronavirus continues to become a concern for scientists and health experts, a study has found that two shots of Pfizer-BioNTech vaccine provide effective protection against all variants and reduce the risk of hospitalisation, significantly.

The study conducted by Kaiser Permanente and Pfizer, which was published in the health journal ‘The Lancet’, concluded that two Pfizer-BioNTech doses are 90% effective against hospitalisations for all variants, including Delta, for at least six months.

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However, the effectiveness of the Pfizer vaccine against all SARS-CoV-2 infections declined over the study period. It declined to 88% within one month of getting vaccinated while in six months, the protection rate was reduced to 47%. 

But the vaccine protection against hospitalisation remained at 90% overall and for all variants, the study said.

For the findings, the researchers analysed 3,436,957 electronic health records from the Kaiser Permanente Southern California (KPSC) health system between the time period of December 4, 2020, and August 8, 2021.

Among the subjects, some 5.4% people were infected with COVID-19 and among the infected ones, 6.6% were hospitalised. All the subjects of the study are from the United States.

The study also shed light on the dominance of the Delta variant of the coronavirus in the US as the proportion of infected cases credited to the Delta variant increased from 0.6% in April 2021 to nearly 87% by July 2021.

The shift in numbers was an indication that the Delta variant had become the dominant strain in the United States.

Meanwhile, the effectiveness of Pfizer-BioNTech shots against the contagious Delta variant one month after the vaccination stood at 93% and fell to 53% after four months. Effectiveness against other variants at one month after receiving two doses was 97% and declined to 67% after four months.

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But the good news is that the protection against Delta-related hospitalisations from the vaccine remained high (93%) for the duration of the study period.

The authors, however, note that analyses with longer follow-up to measure the rate of waning for Delta compared to other variants are warranted.