Researchers from the All India Institute of Medical Science (AIIMS) have published a study in the Lancet that pegs the effectiveness of Bharat Biotech's Covaxin, designated as BBV152, at 50 per cent against symptomatic COVID-19. The finding follows close on the heels of another study, also published in the Lancet, that shows an effectiveness of 77.8 per cent against any severity of COVID-19. The authors note that the finding should be interpreted in the context of a surge setting, and it indicates the need for a rapid rollout of both doses of vaccines, as well as continued implementation of social distancing, sanitisation and the use of masks to restrict the pandemic.
The difference in the numbers of the observational testing and the clinical trial are not cause for alarm. Prof Naveet Wig, Head of Medicine at AIIMS, New Delhi explains, "Our results demonstrated vaccine effectiveness of 50 per cent against symptomatic RT-PCR positive SARS-CoV-2 infection, 2 weeks after complete vaccination, which further increased to 57 per cent at 6 weeks post complete vaccination. In fact, the effectiveness reached 75 per cent towards the end of the study when cases and test positivity rates were declining. It is important not to get fixated with varying effectiveness figures obtained from different studies under different conditions. Addressing vaccine hesitancy by availability of a safe and effective vaccine and achieving good pace and coverage are crucial to control the pandemic with universal vaccination. The data available till now clearly shows effectiveness and safety of Covaxin and the roll out should be continued and accelerated."
The data used in the study was collected between April 15 and May 15, 2021. At the time the study was conducted, there was limited published data on the efficacy of Covaxin. This is the first real world observational testing of the effectiveness of the vaccine, as against controlled clinical trials. The study was conducted during a spike in cases, considered to be the second wave of the pandemic in India, when the delta variant of the SARS-CoV-2 virus was prominent. The study indicates the possibly immune evasive nature of the delta variant.
Considering the conditions under which the observational study was conducted, the findings actually indicate the effectiveness of the vaccine, even during a surge in cases and the circulation of the delta variant, which is likely to be immune evasive. Dr Manish Soneja, Additional Professor of Medicine at AIIMS, New Delhi said, "This is the first vaccine effectiveness study after approval of Covaxin which is an essential component of any vaccine roll-out program. It was carried out in early days of vaccine initiation amongst high-risk population (hospital employees) in the background of a surge dominated by a new highly infectious variant of the virus (delta variant). Vaccine effectiveness demonstrated under such conditions is reassuring of its effectiveness for large scale use."
The study estimates an effectiveness of 50 per cent against symptomatic COVID-19 cases, after an interval of at least 14 days after the administration of both doses, at 46 per cent at least 28 days before testing, and 57 per cent after an interval of at least 42 days before testing. The effectiveness was estimated to be at 47 per cent after an interval of 14 days after excluding participants with previous SARS-CoV-2 infections. A trend was identified at a higher effectiveness in females (after an interval of 14 days) at 66 per cent as against 38 per cent in males, but the study authors note that this is not significant.
The study was conducted in a high risk population, and the differences of effectiveness in the sexes can potentially be attributed to the different roles for females and males in the hospital, as against any biological differences. The effectiveness of the vaccine by the AIIMS team is lower than the effectiveness of the phase 3 trials of the vaccine. The researchers note that there are several factors that can be responsible for the lower effectiveness in the study, as compared to the phase 3 trial.
The study was conducted during a surge of cases in both the hospital and the general population of Delhi. The test positivity rate was at 35 per cent in Delhi on April 26, 2021, which is the highest on record since the outbreak of the pandemic. As such, the study may only represent the effectiveness of the vaccine under surge conditions. The effectiveness could have been driven further down by the circulation of the delta variant, which is considered to be a "variant of concern". The phase 3 trials were conducted when the test-positivity rate was low, and the prevalence of the delta variant among the positive cases was mostly unknown.
The results provide additional evidence that it takes a couple of weeks, or at least 14 days for the effectiveness of the vaccine to build up, and both the doses are required for maximum effectiveness. The study also indicates a modest amount of effectiveness after just a single dose, and underscores the need for a rapid rollout of the vaccines. The data is consistent with the data from other studies and the different vaccine platforms. The study also indicates that apart from the vaccines, the continued implementation of non-pharmacological measures is necessary for restricting the spread of the virus, including social distancing, frequent sanitisation of touch points, and the use of face masks.
Bharat Biotech's Covaxin is one of the two vaccines used by India in its immunisation drive against COVID-19, which began in January 2021. The other vaccine used in the drive is the Oxford–AstraZeneca ChAdOx1 nCoV-19, or Covishield. Both the vaccines use different strategies to evoke the immune response from the body and train it to fight off the SARS-CoV-2 virus. Serum Institute's Covishield is based on a modified chimpanzee adenovirus used as a vector, while Bharat Biotech's Covaxin is a whole virion inactivated vaccine.
The reduced ineffectiveness of the vaccine during surge conditions is also supported by the studies of the effectiveness of another whole virion inactivated vaccine, CoronaVac which showed mixed results under surge conditions in Brazil, which were also conducted under surge settings, with the gamma variant of the SARS-CoV-2 virus circulating. The estimated effectiveness of Covaxin under surge conditions with a variant of concern in circulation is modestly higher than CoronaVac.
The data from the product development and clinical trials of Covaxin have been published in ten peer reviewed journals, making Covaxin one of the most highly published Covid-19 vaccines in the world. On November 12, Bharat Biotech announced the safety and efficacy analysis of phase 3 trials. The trial involved 25,800 volunteers in 25 sites in India, making it India's largest clinical trial for a Covid-19 vaccine.
The phase 3 trials pegged the effectiveness of Covaxin at 77.8 per cent against symptomatic Covid-19 patients, 93.4 per cent against sever symptomatic Covid-19 patients and 63.6 per cent against asymptomatic Covid-19 patients. The effectiveness was estimated at 65.2 per cent against the delta variant of the Sars-CoV-2 virus, but the study authors indicated that there was further testing needed to support this finding, and investigate the effectiveness against other variants.
Dr Balram Bhargava, Director General, Indian Council of Medical Research (ICMR), said, "The bench to bedside journey of Covaxin in less than 10 months showcases the immense strength of 'Atmanirbhar Bharat' along with the Indian academia and industry in fighting against the odds and carving a niche in the global community."
The World Health Organisation granted emergency use listing to Covaxin on November 3, enabling countries to fast track the regulatory approvals necessary for importing the vaccine. Over 150 million doses of the vaccine have been manufactured, which is an important contributor to the global fight against the coronavirus. Bharat Biotech has indicated that it is on track to achieve an annualised capacity of about 1 billion doses by the end of 2021. Currently, there are ongoing controlled clinical trials of Covaxin among children between two and eighteen years of age with the results expected to be available in the fourth quarter of 2021.
No comments:
Post a Comment