The effectiveness of SARS-CoV-2 vaccination in preventing severe illness and death – real-world data from a cohort of patients hospitalized with COVID-19

BackgroundDue to the unprecedented speed of SARS-CoV-2 vaccine development, their efficacy trials and issuance of emergency use approvals and marketing authorizations, additional scientific questions remain that need to be answered regarding vaccine effectiveness, vaccination regimens and the need for booster doses. While long-term studies on the correlates of protection, vaccine effectiveness, and enhanced surveillance are awaited, studies on breakthrough infections help us understand the nature and course of this illness among vaccinated individuals and guide in public health preparedness.MethodsThis observational cohort study aimed at comparing the differences in clinical, biochemical parameters and the hospitalization outcomes of 53 fully vaccinated individuals with those of unvaccinated (1,464) and partially vaccinated (231) individuals, among a cohort of 2,080 individuals hospitalized with SARS-CoV-2 infection.ResultsCompleting the course of vaccination protected individuals from developing severe COVID-19 as evidence by lower proportions of those with hypoxia, abnormal levels of inflammatory markers, requiring ventilatory support and death compared to unvaccinated and partially vaccinated individuals. There were no differences in these outcomes among patients who received either vaccine type approved in India.ConclusionWith a current rate of only 9.5% of the Indian population being fully vaccinated, efforts should be made to improve the vaccination rates as a timely measure to prepare for the upcoming waves of this highly transmissible pandemic. Vaccination rates of the communities may also guide in the planning of the health needs and appropriate use of medical resources.Research in contextEvidence before this studyThe Government of India started vaccinating its citizens from the 16thof January 2021, after emergency use authorization had been received for the use of two vaccines, BBV152, a COVID-19 vaccine based on the whole-virion SARS-CoV-2 vaccine strain NIV-2020-770, (Covaxin) and the recombinant replication-deficient chimpanzee adenovirus vector encoding the spike protein ChAdOx1 nCoV-19 Corona Virus Vaccine (Covishield). These have been approved by the Indian regulatory authority based on randomized controlled studies. In these studies, was found that the vaccines led to more than 90% reduction in symptomatic COVID-19 disease. However, there is scarce evidence of the efficacy of these vaccines in real-world scenarios. A few studies have looked at vaccinated cohorts such as health care workers in whom the vaccines had an efficacy similar to the RCTs. In a study of patients with SARS-CoV-2 infection admitted to a tertiary care hospital in New Delhi, it was found that mortality in fully vaccinated patients was 12.5% as compared to 31.5% in the unvaccinated cohort.Added-value of this studyThis cohort of hospitalized patients with SARS-CoV-2 infection was studied during the peak of the second wave of COVID-19 in India during which the delta variant of concern was the predominant infecting strain and had 26% patients who were partially vaccinated and 71.4% who were unvaccinated. Only 3% of the patients were fully vaccinated and developed a breakthrough infection. At the time of presentation, 13% of the individuals with breakthrough infection and 48·5% in the non-vaccinated group were hypoxic. Inflammatory markers were significantly lower in the completely vaccinated patients with breakthrough infection. The need for use of steroids and anti-viral agents such as remdesivir was also significantly low in the breakthrough infection group. A significantly less proportion of the individuals with breakthrough infection required oxygen supplementation or ventilatory support. Very few deteriorated or progressed to critical illness during their hospital stay. Only 3 individuals (5.7%) out of the 53 who developed breakthrough infection succumbed to illness while case fatality rates were significantly higher in the unvaccinated (22.8%) and partially vaccinated (19.5%) groups. Propensity score weighted multivariate logistic regression analysis revealed lower odds of developing hypoxia, critical illness or death in those who were completely vaccinated.Implications of all the available evidenceThe real-world effectiveness of the vaccines against SARS-CoV-2 seems to be similar to the randomized controlled trials. The vaccines are very effective in reducing the incidence of severe COVID-19, hypoxia, critical illness and death. The reduced need for oxygen supplementation, mechanical ventilation and the requirement of corticosteroids or other expensive medications such as anti-viral drugs could go a long way in redistributing scarce health care resources. All nations must move forward and vaccinate the citizens, as the current evidence suggests that ‘prevention is better than cure’.