None of the nearly 600 vaccine recipients reportedly required hospitalization.
In an indicator of the declining role of vaccines in preventing coronavirus transmission, just over 25% of fully vaccinated healthcare workers at a Delhi hospital contracted a new or “advanced” infection. However, none of the nearly 600 vaccine recipients required hospitalization. Although previous reports of similar infections have been reported in other studies in India, this is the first time that such a high percentage has been reported as part of a single study.
The study included health workers from the Max group of Delhi and Gurugram hospitals and was led by scientists from the Institute of Genomics and Integrative Biology of the CSIR (CSIR-IGIB). It appears as a prepress and has not yet been peer-reviewed.
The time between the first and second dose varied, but 482 received the second dose 42 days after the first dose. Approximately half of the recipients had been previously infected with SARS-CoV-2.
Antibody levels
To confirm reinfection, the researchers relied on levels of antibodies directed to the nucleocapsid region of the coronavirus, which is different from the region (tip protein) to which vaccine-generated antibodies normally target. Currently, all vaccines are designed to produce spike-protein antibodies, and therefore high levels of antibodies against the nucleocapsid region were considered markers of a new coronavirus infection. An advanced infection is one in which someone tests positive at least two weeks after their second dose.
Shantanu Sengupta of the CSIR-IGIB and one of the scientists who led the study said 25% was a “conservative estimate,” as many of the infections were probably asymptomatic and that only a subset of them were likely to show symptoms. the test would be done.
Although the infections were mild, it could contribute to health workers infecting patients unknowingly, Dr. Sengupta said. For their analysis, the scientists relied on blood samples taken each week (up to 90) after vaccination and because this period coincided with the second wave in India, where most infections went away. due to the Delta variant, it was most likely that these advanced infections were also due to the Delta variant. “Two doses of the vaccine were not protective against infection, but infection followed by vaccination (even a single dose) was significantly protective against new infections,” he added.
At present, Delta and its associated lineages account for almost half of coronavirus infections and are believed to drive the infection in Kerala and Maharashtra.
Health workers who were previously infected had a reinfection rate of 2.5% during the same period.
According to emerging evidence from several countries such as the United States and Israel where, despite vaccination of half the population, advanced infections are reported, the study stresses that India may also not be immune to phenomenon.
“The neutralization of the Delta variant by antibodies against non-Delta ear protein is considerably reduced. This means that neither previous infection by non-Delta variants nor existing vaccines are sufficient individually for the pathway to herd immunity. This also implies that masking is an essential part of any rational COVID control strategy, as it is agnostic to immune leakage, ”the authors note in their study.
The data indicate the “urgency to explore routes toward more effective use of vaccines,” the authors say. Because a single dose of ChAdOx1-nCoV19 in previously infected subjects induces humoral immunity comparable to or better than two doses in naïve subjects, a single dose could be optimally targeted to populations with high seropositivity.