A recent research on the effectiveness of two doses of severe acute respiratory syndrome Coronavirus 2 (SARS-CoV-2) for COVID-19 vaccine conducted in Guangzhou, China, has proven that it provides sufficient protection against the deadly spread of the Delta variant worldwide.
Guangzhou Center for Disease Control and Prevention Chinese epidemiologist lead researcher Zhong Nanshan found that two shots of the vaccine provided an efficacy of 59% (six out of 10 patients) against COVID-19 caused by the Delta variant, 70.2% (seven out of 10 patients) against a moderate form of the disease and 100% against severe cases.
This implies that the vaccine is more effective against moderate COVID-19 than mild COVID-19. In this regard, the research also exceeded the threshold decided by the World Health Organisation (WHO) to reach the standard that any vaccine for SARS-CoV-2 must achieve the efficacy of 50%.
The research polled data from 628 participants, including 153 COVID-19 patients infected by the Delta variant and 475 close contact cases in the city. The patients were 18 to 59 years old. Of them, 10 had critical symptoms, six had severe symptoms, 105 had moderate symptoms, and 32 had mild symptoms.
Two inactivated vaccines, CoronaVac manufactured by Sinovac Biotech Ltd and the China National Biotec Group SARS-CoV-2 vaccine, were chosen by researchers to measure the effectiveness against the Delta strain among the patients.
Test for effectiveness
The effectiveness of the vaccines was determined using a test-negative case-control design, a popular method for evaluating vaccine efficacy. The vaccines have also been adopted for mass vaccination within mainland China.
The severity or mildness of the COVID-19 symptoms was categorised based on the observation of patients. Those without any external signs were classified as mild COVID-19 patients; however, those with respiratory symptoms such as fever and imaging characteristics of pneumonia were grouped as moderate COVID-19 patients.
Patients with oxygenation index <300 mmHg, resting oxygen saturation <93%, and respiratory rate >30/min were categorised as severe. Those experiencing respiratory failure and requiring mechanical ventilation, shock or other organ failure requiring admission to the ICU were classified as critical COVID-19 patients.
The research also revealed that those patients vaccinated with a single vaccine dose also showed some degree of protection against the COVID-19 disease. The effectiveness of a single dose of the vaccine was 13.8%. The study found that none of the 16 cases with critical and severe COVID-19 had been vaccinated with SARS-CoV-2 vaccines.
In the same research, the scientists also discovered that the vaccine effectiveness was higher in females and people in the age group of 40-59 (with an efficacy rate of 72.5%) compared to males and those with moderate COVID-19. This shows the need to further strengthen vaccination of females and the elderly in the continuing vaccination programme.
In light of this research, countries that are facing severe shortage of COVID-19 vaccines especially are able to use this research-backed information to make vaccine policies, which may require double-dose vaccination coverage in advance as this would prioritise unaffected individuals before another outbreak occurs.
Dr Ajit Pal Singh Raina is a Vaccine Specialist of Pharmaniaga Berhad. He is a medical doctor by training with a postgraduate degree in Public Health and a Doctoral degree in Infectious Disease Epidemiology with over 20 years of experience in the Biopharmaceuticals industry, especially vaccines. To date, Dr Ajit has conducted numerous clinical studies in Asia, Africa and South America, resulting in vaccine prequalification/approvals from WHO. He has multiple vaccine publications in reputed journals such as Lancet, NEJM and Human Vaccines.
(The views expressed in this article are those of the author(s) and do not reflect the official policy or position of Bernama.)
Keywords: covid-19, Guangzhou, sinovac, vaccine, effectiveness, delta, variant