A staff member checks tags on vials of COVID-19 vaccine at a packing line of Sinovac Life Sciences Co., Ltd. in Beijing, capital of China, Dec 23, 2020.Photo:Xinhua

Chinese vaccine manufacturer SINOVAC released real-world data on the company's COVID-19 vaccine, CoronaVac, addressing the vaccine's safety and efficacy for seniors, a key target group for China's continued push to improve vaccination rates, particularly for those aged 80 or above. 
According to materials the Global Times obtained from SINOVAC, the results of a phase 1/2 clinical trials and a study using CoronaVac as booster shots conducted in healthy seniors aged 60 and over in China showed that the vaccine was safe for the country's elderly population, and there were no grade 3 adverse reaction reports, or vaccine-related serious adverse events (SAE) reports.

A third dose of the vaccine quickly induced a strong immune response in people aged 60 and above. The geometric mean titer (GMT) of the antibody in the serum rose to 305 on the seventh day after the administration of a third dose, which was a seven-fold increase from the antibody GMT level at 28 days following the second dose.

A number of overseas clinical or real-world studies also showed encouraging signals. A study of 2,000 medical staff and community workers in Chile (30 percent aged ≥60 years, 45 percent suffering from chronic diseases) after vaccination with CoronaVac under two different immunization programs concluded that both programs demonstrated safety and immunogenicity, and the incidence of adverse events was lower in elderly volunteers compared with younger populations.

A study in Brazil among elderly people aged 65-101 (95.6 percent suffering from chronic diseases) showed that adverse events after each dose of basic immunization were mild to moderate, and there were no serious adverse events related to the vaccine. In Colombia, a real-world study of two doses of Sinovac's COVID-19 vaccine for seniors over 60 years old showed that the vaccine offered a good protective effect in aged populations, and the death protection rates for people aged 60-69, 70-79, and 80 years old were respectively 83.3 percent, 78.1 percent and 66.3 percent.

In Hong Kong Special Administrative Region, a study on elderly people aged 60 years and above who had accepted different doses of COVID-19 vaccine showed that, compared with the baseline period, the risk of adverse events of special concern in the elderly aged 60 years or above after vaccination had not significantly increased. The benefits of vaccination far outweigh the risks when compared to COVID-19 complications observed in previous studies for those aged 60 or older, according to the study.

Another population-based ecological study in the context of the prevalence of the Omicron variant strain in Hong Kong showed that the third COVID-19 vaccine provided additional protection to adults, especially those over 60 years old and other high-risk groups. After a third dose is administered to people over 60 years old, the protective effect of preventing severe cases is as high as 88 percent and the protective effect of preventing death cases is as high as 93 percent, according to SINOVAC.

A third case-control study among people over 60 years old in Hong Kong showed that SINOVAC's COVID-19 vaccine can effectively protect the elderly from infection and severe diseases during the domination of the BA.2 strain. Three doses of the vaccine can provide 53.9 percent protection against infection, 86.7 percent protection in preventing COVID-19-related hospitalization, 89.8 percent protection in preventing severe COVID-19 complications, and 95.0 percent protection effective in preventing COVID-19-related death in people aged 80 and above.

CoronaVac is also safe and effective for people with underlying diseases, SINOVAC said.

For cancer patients, a prospective, multi-center cohort study conducted in Turkey showed that Sinovac's vaccine offered good safety and immunogenicity for cancer patients. The incidence of side effects reported after the first dose in the control group was significantly higher than that in cancer patients. The incidence of side effects after the first dose was 15.9 percent in the patient group and 22.5 percent in the control group. The seropositive rate of the cancer patient group was 85.2 percent, and the seropositive rate of the control group was 97.5 percent. The high seropositive rate of cancer patients indicates that vaccination of cancer patients can effectively prevent COVID-19 infection, according to SINOVAC.

For the chronically ill population, SINOVAC said that a review in China of patients (≥40 years old) with one of six common chronic diseases (coronary heart disease, hypertension, diabetes, chronic respiratory disease, obesity, and cancer) has shown that on days 14-28 after vaccination, except for patients with cardiovascular disease and chronic respiratory disease, there was no significant difference in neutralizing antibody levels between the disease group and the healthy control group. There was no significant difference in overall safety, and the most frequently reported adverse events in the six disease groups were the same as those in the healthy control group, with the main adverse events being pain and fatigue at the injection site. Amongst elderly populations, patients with chronic diseases and healthy groups showed no significant differences in adverse events after vaccination of full procedure (15.58 percent vs. 11.11 percent), the first dose (9.71 percent vs. 6.48 percent) or the second dose (9.93 percent vs. 6.48 percent).

Zheng Zhongwei, director of the Development Center for Medical Science and Technology of the National Health Commission (NHC), had said that China's COVID-19 vaccines are very safe for seniors. According to incomplete global statistics, people over the age of 60 have collectively received over one billion doses of Chinese produced vaccines, and all of them are very safe, with the highest age for vaccination being 106 years old.

Those aged 80 years old or above who decline to be vaccinated face a risk of death of about 14.7 percent; if they get one shot, the risk of death drops to 7.16 percent. The risk would drop to 1.5 percent after three shots. Therefore, compared with no vaccination, the risk of death was reduced by 9.3 times after receiving three doses of the vaccine, according to Zheng.

Seniors aged over 60 are at risk of severe illness after being infected, especially the elderly over the age of 80. In clinical practice, people with underlying diseases also have a higher risk of severe illness after being infected. Guo Yanhong, another NHC official, had suggested that "vaccination can effectively reduce the risk of severe illness and death. It is recommended that people without contraindications and eligible for vaccination, especially the elderly, should receive the vaccines as soon as possible."