Researchers in China have reported the results of a phase I / II clinical trial showing that the CoronaVac vaccine candidate is getting up well in older people and effectively generating antibody responses. face severe respiratory coronavirus syndrome 2 (SARs-CoV-2) – the causative agent of coronavirus disease 2019 (COVID-19).
CoronaVac is an inactive SARS-CoV-2 vaccine developed by the Chinese pharmaceutical company Sinovac Life Sciences based in Beijing, China.
Writing in Lancet infectious diseases, the team says this is the first report of inactivated SARS-CoV-2 vaccine tested in older adults (age 60 years or older). The findings support practice in this elderly population.
Weidong Yin from Sinovac Biotech and colleagues say all the side effects of the vaccine were mild or moderate, with the most common being pain at the site of the injection.
Further studies are now needed to confirm the effectiveness of Coronavac in inhibiting COVID-19 in older adults, the team said.
The study is ongoing and is registered with ClinicalTrials.gov (NCT04383574).
Older people are at increased risk of COVID-19 infection and death
Research has shown that people aged 60 and over are at increased risk of serious illness and death from COVID-19, especially if they have underlying health conditions.
There is therefore an urgent need for a vaccine that will protect older people against COVID-19.
However, the response to vaccination is often reduced in older adults as a result of age-related changes that affect both the textured and altered immune systems – something called immunosenescence.
More about CoronaVac
“Purified inactivated viruses have traditionally been used for vaccine development, and there are currently eight COVID-19 candidate inactivated vaccines in clinical evaluation,” said Yin and team.
Although efficacy results are not yet available, studies have shown that these vaccines stimulate antibody responses against SARS-CoV-2 and have good safety profiles.
The researchers previously reported the results of a phase I / II clinical trial of CoronaVac in participants aged 18-59 years.
The results showed that CoronaVac was recovering well and stimulating humoral responses against SARS-CoV-2. Seroconversion levels ranged from 92% to 100% after two doses of CoronaVac (3 µg and 6 µg) administered 2 or 4 weeks apart.
What did the current study cover?
Now, the team has conducted a randomized, double-blind, placebo-controlled, I / II clinical trial to evaluate the safety, tolerability, and immunogenicity of CoronaVac in adults age 60 years and older.
“This is the first report of an inactivated SARS-CoV-2 vaccine, CoronaVac, that has been tested in older adults (age 60 years or older),” wrote Yin and colleagues.
In Phase I there were 72 participants, average age of 65 · 8 years, enrolled between 22 Maynd and June 1stst, 2020. In Phase II there were 350 participants, average age of 66 · 6 years, enrolled between 12 Juneth and 15 Juneth, 2020.
For phase 1, a dose-enhancing study was performed with randomly assigned participants to receive 3 µg or 6 µg doses of CoronaVac or placebo 28 days apart.
For phase 2, participants were randomly assigned to receive 1 · 5μg, 3µg, or 6µg doses of CoronaVac or placebo 28 days apart.
Adverse endpoint was the main safety point within 28 days after each injection. The main endpoint of immunogenicity was seroconversion level 28 days after the second injection.
Seroconversion has been defined as a shift from baseline seronegativity to seropositivity for neutralization of antibodies against live SARS-CoV-2. For those who were seropositive at baseline, seroconversion was defined as a fourfold increase in anti-SARS-CoV-2 neutralizing antibody titer.
What are the conclusions?
The researchers found that two doses of CoronaVac were safe and well tolerated at doses of 1 · 5μg, 3μg, and 6μg in adults 60 years and older.
“The results were similar to our study of adults aged 18-59,” the team says.
Across all stages, adverse reactions occurred within 28 days of injection at a rate of 20% in the 1 · 5μg group, 20% in the 3μg group, 22% in the 6μg group, and 21% in the placebo group.
“The incidence of adverse reactions in different dose groups was similar, indicating that there were no safety-related dose concerns,” wrote Yin and colleagues.
In addition, all moderate or severe adverse effects in depth and pain at the injection site were the most frequently reported event (9%).
The researchers say, “CoronaVac is safe and patient enough in older adults.”
What about immunogenicity?
At stage I, seroconversion was observed in 24 of 24 (100%) participants in the 3μg group and in 22 of 23 (95 · 7%) participants in the 6μg group.
At stage 2, seroconversion was observed in 88 of 97 (90.7%) participants in the 1 · 5μg group, 96 of 98 (98.0%) in the 3μg group, and 97 of 98 (99 · 0 %) participants in the 6μg group.
“Among the three doses evaluated, the neutralizing antibody titers induced by the 3μg dose were similar to those in the 6μg dose and higher than the 1 · 5μg dose,” wrote Yin and colleagues .
“Along with the safety and production potential, the 3μg dose of CoronaVac with a two-dose vaccine schedule is used in the ongoing phase 3 trials to assess protection against COVID-19,” the team says.