CoronaVac Vaccine from Sinovac: Assessing Safety and Potential Adverse Reactions
The CoronaVac vaccine, developed by Sinovac Biotech, continues to be a significant player in the global fight against COVID-19. Recommended for individuals aged 18 years and above, this inactivated virus vaccine has been approved for use in 52 countries.
Phase 1 and 2 clinical trial data for the CoronaVac vaccine reveal that the most common side effect reported within 28 days of the second dose was injection-site pain. Other common side effects included fatigue, diarrhea, and muscle pain, most of which were mild and lasted only for 2 days.
Current research indicates that booster shots with the CoronaVac vaccine can effectively reactivate immune memory, though their effectiveness specifically against the Omicron variant varies among studies.
Key findings from recent studies are as follows:
- A prospective longitudinal cohort study evaluated the effectiveness of a delayed homologous CoronaVac booster and found that it effectively reactivated immune memory and enhanced immune response, indicating the booster’s benefit in reinforcing immunity in previously vaccinated individuals.
- A Brazilian phase 3 PROFISCOV trial post-unblinding analysis provided insights into the long-term efficacy and immune responses of CoronaVac among healthcare workers, confirming its continued protective effect over time, though detailed variant-specific effectiveness (e.g., Omicron) was not specified.
- Another clinical scenario from a case study noted that after two doses of CoronaVac, humoral immune response (anti-SARS-CoV-2 IgG) was robustly elicited, but neutralizing antibodies targeting receptor-binding domains, which are crucial for blocking virus entry, were not fully positive, suggesting partial immune escape or lower neutralization capacity especially relevant for variants like Omicron.
- Comparative studies highlight that other booster platforms, such as the Convidecia viral vector vaccine administered orally as a booster, induced a more robust immune response than homologous CoronaVac boosters in people initially vaccinated with two CoronaVac doses, suggesting that heterologous boosting might enhance immunity against evolving variants including Omicron.
- There was a Phase 4 clinical trial comparing CoronaVac booster with alternative platforms (Convidecia injection vs inhaled, protein subunit vaccines), though detailed results specifically on Omicron neutralization were not available. Next-generation vaccines aiming for broader variant coverage (including pancoronavirus vaccines) are under development but not yet widely available.
The WHO recommends the CoronaVac vaccine for people living with HIV. According to data from a Brazilian trial, CoronaVac has an efficacy rate of 50.4% for preventing symptomatic infection. The WHO's Emergency Use Listing (EUL) procedure for CoronaVac included a review of the vaccine's safety and efficacy, as well as "onsite inspections of the production facility."
As of January 2022, research suggests that while CoronaVac booster doses can boost immune memory and improve immunity, heterologous boosters (such as Convidecia) may provide stronger protection against Omicron, which partially evades neutralizing antibodies from inactivated vaccines. Research is ongoing to develop next-generation vaccines with broader variant-proof efficacy.
Until studies have adequately evaluated the safety of CoronaVac in pregnant individuals, the WHO recommends its use when the benefits of vaccination outweigh the potential risks. Participants who received CoronaVac reported a lower occurrence of fever in comparison to other COVID-19 vaccines, including the mRNA-based vaccine from Moderna and viral vector vaccines from Oxford-AstraZeneca and CanSino.
However, a paper published in January 2022 indicates that two doses of CoronaVac could not neutralize the Omicron variant. Adding a booster dose of the Pfizer-BioNTech mRNA vaccine somewhat improved the immune response to the Omicron variant, but participants had significantly reduced neutralization antibodies against Omicron compared with those produced against the Delta variant.
Individuals with a history of anaphylaxis to any of the vaccine's ingredients should not receive the CoronaVac vaccine. Sinovac plans to continue its clinical trials to determine the efficacy and timing of the booster shot, as well as the vaccine's effectiveness against emerging SARS-CoV-2 variants. The COVID-19 vaccine CoronaVac is produced by Sinovac Biotech, a China-based pharmaceutical company headquartered in Beijing.
- In the global health-and-wellness efforts against COVID-19, the inactivated virus vaccine, CoronaVac by Sinovac Biotech, has been approved for use in 52 countries, and its booster doses could potentially improve immunity.
- Following the administration of two CoronaVac vaccine doses, there are concerns about partial immune escape or lower neutralization capacity, particularly against the Omicron variant, prompting ongoing research into next-generation vaccines with broader variant-proof efficacy.
