Efficacy data of CoronaVac in Turkey – Authors’ response


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We thank Martina McMenamin and Benjamin Cowling for raising important questions about vaccine trials in the context of our article.
1
  • Tanriover MD
  • DoÄŸanay HL
  • Akova M
  • et al.
Efficacy and safety of an inactivated whole virion SARS-CoV-2 vaccine (CoronaVac): interim results from a double-blind, randomized, placebo-controlled phase 3 trial in Turkey.

The work to which they refer by Palacios and his colleagues

2
  • Palacios R
  • Batista AP
  • CSN Albuquerque
  • et al.
Efficacy and safety of an inactivated COVID-19 vaccine in healthcare professionals in Brazil: the PROFISCOV study.

has not been published in a peer-reviewed journal; therefore, we cannot comment on the accuracy or comparability of its methods. Data from Indonesian trials has been published,

3
  • Fadlyana E
  • Rusmil K
  • Tarigan R
  • et al.
Phase III, Observer-Blind, Randomized, Placebo-Controlled Study of the Efficacy, Safety and Immunogenicity of Inactivated SARS-CoV-2 Vaccine in Healthy Older Adults from 18 to 59 years old in Indonesia.

and although the primary method for this study was similar to ours, the COVID-19 case definition and methods used for active surveillance were different. Only 1,620 volunteers were included, but over a longer follow-up period (approximately 2.5 months) preventing a direct comparison of the primary endpoint.

3
  • Fadlyana E
  • Rusmil K
  • Tarigan R
  • et al.
Phase III, Observer-Blind, Randomized, Placebo-Controlled Study of the Efficacy, Safety and Immunogenicity of Inactivated SARS-CoV-2 Vaccine in Healthy Older Adults from 18 to 59 years old in Indonesia.

Nonetheless, the efficacy of CoronaVac against serious illness in this study was 100% as there were no critical cases or deaths attributable to COVID-19, which is undoubtedly similar to our results.

Regarding post-vaccination neutralizing antibody titers in the immunogenicity subset of our trial, the seroconversion rate was 89.7% in the vaccinated group, of which 92% had neutralizing antibodies. This result could translate into a positivity of neutralizing antibodies of 82.5% in these volunteers. The efficacy against symptomatic disease reported at 83.5% is consistent with this immunogenicity result. We have carried out active surveillance to detect COVID-19 in patients; However, as the primary outcome measure was symptomatic COVID-19, it is indeed possible that we missed asymptomatic patients. In fact, most COVID-19 vaccine trials aim for a similar outcome, focusing on effectiveness in preventing symptomatic and serious illness rather than preventing infection. We were aware of the short follow-up period in our interim review and therefore discussed it as a major limitation of the article,
1
  • Tanriover MD
  • DoÄŸanay HL
  • Akova M
  • et al.
Efficacy and safety of an inactivated whole virion SARS-CoV-2 vaccine (CoronaVac): interim results from a double-blind, randomized, placebo-controlled phase 3 trial in Turkey.

indicating that the study would not allow commenting on long-term protection.

Real-world efficacy data from pragmatic study designs will add value to Phase 3 trials to see vaccine performance in unselected populations, as complementary studies rather than concurrent. For example, Jara and her colleagues
4
  • Jara A
  • Undurraga EA
  • González C
  • et al.
Efficacy of an inactivated SARS-CoV-2 vaccine in Chile.

reported analysis of actual data from Chile, including approximately 10.2 million people vaccinated with CoronaVac. The adjusted vaccine efficacy among fully immunized individuals was 65.9% (95% CI 65.2 to 66.6) for the prevention of COVID-19 and 87.5% (86.7 to 88 , 2) for prevention. admission to hospital.

During a pandemic where only 2.3% of people in low-income countries had received at least one dose of a COVID-19 vaccine by October 2021, every effort to make safe COVID-19 vaccines available is valuable . We believe our data is an important contribution to the scientific literature in a world where we can no longer establish randomized, placebo-controlled trials for COVID-19 vaccines for ethical reasons. The way forward to building confidence in vaccines is to communicate real world data transparently.

We do not declare any competing interests.

The references

  1. 1.
    • Tanriover MD
    • DoÄŸanay HL
    • Akova M
    • et al.

    Efficacy and safety of an inactivated whole virion SARS-CoV-2 vaccine (CoronaVac): interim results from a double-blind, randomized, placebo-controlled phase 3 trial in Turkey.

    Lancet. 2021; 398: 213-222

  2. 2.
    • Palacios R
    • Batista AP
    • CSN Albuquerque
    • et al.

    Efficacy and safety of an inactivated COVID-19 vaccine in healthcare professionals in Brazil: the PROFISCOV study.

    SSRN. 2021; ()

  3. 3.
    • Fadlyana E
    • Rusmil K
    • Tarigan R
    • et al.

    Phase III, Observer-Blind, Randomized, Placebo-Controlled Study of the Efficacy, Safety and Immunogenicity of Inactivated SARS-CoV-2 Vaccine in Healthy Older Adults from 18 to 59 years old in Indonesia.

    Vaccine. 2021; 39: 6520-6528

  4. 4.
    • Jara A
    • Undurraga EA
    • González C
    • et al.

    Efficacy of an inactivated SARS-CoV-2 vaccine in Chile.

    N Engl J Med. 2021; 385: 875-884

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