From the Authors:
We thank Mungmunpuntipantip and Wiwanitkit for their interest in our recent work published in the Journal (1). In our randomized clinical trial (RCT) study, we concluded that both the CoronaVac and BNT162b2 vaccines boosted antibody responses in CoronaVac-immunized individuals, but BNT162B2 was markedly superior in immunogenicity. Although Mungmunpuntipantip and Wiwanitkit commented that an inactivated vaccine should not be used as a booster or as a booster to standard two-dose regimens, we believe that inactivated vaccines such as CoronaVac are still playing an essential role in controlling the coronavirus disease (COVID-19) outbreak.
First, the supply of mRNA vaccines cannot meet global needs, and the ultralow (−80°C) “cold-chain” requirements may limit their use in many developing countries. Second, we observed that CoronaVac vaccines elicit T-cell responses at least as potent as RNA vaccines (2) and these should provide some protection against severe disease outcomes. Finally, there is a minority of individuals who develop adverse reactions to RNA vaccines, and alternatives are needed.
They also raised the question of whether age, sex, smoking, and history of previous COVID-19 illness may have confounded the outcomes in our study. Our study participants were recruited from a previous study of immunogenicity of the two vaccines 1 month after the second dose, and patient recruitment criteria included absence of prior severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection (2). Furthermore, all patients had blood collected at recruitment and were shown to be sero-negative. This cohort has been followed up since, and none of them had diagnosed SARS-CoV-2 infection. Given the low rates of SARS-CoV-2 transmission in Hong Kong during the period of the study, the likelihood of undiagnosed asymptomatic infection is low. We did in fact confirm that there were no significant differences in age, sex, smoking, and other demographic factors between the two groups, and the data was provided in the supplementary information to our manuscript (https://www.mect.cuhk.edu.hk/paper/Supporting-Information.pdf).
Footnotes
Supported by grants from the Health and Medical Research Fund Commissioned Research on the Novel Coronavirus Disease (COVID-19), Hong Kong SAR (COVID1903003; COVID190126).
Author Contributions: Conception and design, analysis and interpretation, and preparation of the manuscript: C.K.P.M., D.S.H., and M.P.
Originally Published in Press as DOI: 10.1164/rccm.202201-0221LE on May 12, 2022
Author disclosures are available with the text of this letter at www.atsjournals.org.
References
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