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We would like to clarify that the table of the estimates extracted from each of the included studies as mentioned by Prof Cowling has been posted along with the codes in the GitHub link (folder Data), which we have already included in the original main text.
We thank Prof Cowling for pointing out the heterogeneity problem which has already been considered in our review planning and accounted for in our analysis. According to the Cochrane training handbook, source of heterogeneity can be explored by performing subgroup analyses. Hence, we performed subgroup analyses by re-analysing studies that investigated the variable of interest (age, ethnicity, immunocompromised or not, or covid-19 variant) with all other factors controlled. We controlled the co-factors in each subgroup to minimize bias induced in the final estimates, which addressed Prof Cowling’s concern of heterogeneity when pooling results.
We are now amidst the continuing process of updating our living systematic reviews with network meta-analysis with any new and carefully vetted publications in a timely fashion to serve the public.
Yours truly
Wing Ying Au
Peter Cheung
Competing interests:
No competing interests
15 June 2022
Peter Pak Hang Cheung
Assistant Professor
Wing Ying AU
The Chinese University of Hong Kong
Li Ka Shing Medical Sciences Building, Prince of Wales Hospital, 30-32 Ngan Shing Street, Shatin, New Territories, Hong Kong
I was surprised that there was not a single forest plot or table of the estimates extracted from each of the included studies, even in the supplementary materials. This should have been picked up by peer reviewers and would be important to allow reproducibility checks. I was also surprised that authors pooled VE across variants and across age groups when these are well established heterogeneities in VE by age and by variant that would indicate against pooling. There may even be interactions between vaccine type and variant if some vaccine technologies are better than others at providing broad immunity. I'm glad it's a living review and I look forward to seeing updates in the coming months to include a table of the raw extracted values from each study as well as more and more publications reporting VE estimates against Omicron. The comprehensive reference list will be very useful.
Re: Effectiveness of heterologous and homologous covid-19 vaccine regimens: living systematic review with network meta-analysis
Dear Editor
We would like to clarify that the table of the estimates extracted from each of the included studies as mentioned by Prof Cowling has been posted along with the codes in the GitHub link (folder Data), which we have already included in the original main text.
We thank Prof Cowling for pointing out the heterogeneity problem which has already been considered in our review planning and accounted for in our analysis. According to the Cochrane training handbook, source of heterogeneity can be explored by performing subgroup analyses. Hence, we performed subgroup analyses by re-analysing studies that investigated the variable of interest (age, ethnicity, immunocompromised or not, or covid-19 variant) with all other factors controlled. We controlled the co-factors in each subgroup to minimize bias induced in the final estimates, which addressed Prof Cowling’s concern of heterogeneity when pooling results.
We are now amidst the continuing process of updating our living systematic reviews with network meta-analysis with any new and carefully vetted publications in a timely fashion to serve the public.
Yours truly
Wing Ying Au
Peter Cheung
Competing interests: No competing interests