A systematic review of methodological approaches for evaluating real-world effectiveness of COVID-19 vaccines: Advising resource-constrained settings

Abstract

Real-world effectiveness studies are important for monitoring performance of COVID-19 vaccination programmes and informing COVID-19 prevention and control policies. We aimed to synthesise methodological approaches used in COVID-19 vaccine effectiveness studies, in order to evaluate which approaches are most appropriate to implement in low- and middle-income countries (LMICs). For this rapid systematic review, we searched PubMed and Scopus for articles published from inception to July 7, 2021, without language restrictions. We included any type of peer-reviewed observational study measuring COVID-19 vaccine effectiveness, for any population. We excluded randomised control trials and modelling studies. All data used in the analysis were extracted from included papers. We used a standardised data extraction form, modified from STrengthening the Reporting of OBservational studies in Epidemiology (STROBE). Study quality was assessed using the REal Life EVidence AssessmeNt Tool (RELEVANT) tool. This study is registered with PROSPERO, CRD42021264658. Our search identified 3,327 studies, of which 42 were eligible for analysis. Most studies (97.5%) were conducted in high-income countries and the majority assessed mRNA vaccines (78% mRNA only, 17% mRNA and viral vector, 2.5% viral vector, 2.5% inactivated vaccine). Thirty-five of the studies (83%) used a cohort study design. Across studies, short follow-up time and limited assessment and mitigation of potential confounders, including previous SARS-CoV-2 infection and healthcare seeking behaviour, were major limitations. This review summarises methodological approaches for evaluating real-world effectiveness of COVID-19 vaccines and highlights the lack of such studies in LMICs, as well as the importance of context-specific vaccine effectiveness data. Further research in LMICs will refine guidance for conducting real-world COVID-19 vaccine effectiveness studies in resource-constrained settings.

Vaccination and Variants: retrospective model for the evolution of Covid-19 in Italy

“…Fitting rates present in Eq.s (1), whose value is not dependent on time, are given in Table 3. Constants present in Eq.s (3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13), obtained as fitting parameters, are listed in Table 4. Days and intervals of time present in Eq.s (3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13), obtained as fitting parameters are reported in Table 5 (in the simulations the time 0 corresponds to the initial time, t 0 reported in Table 2, i.e.…”

“…At the time writing (31 January 2022) the percentage of Italian population fully vaccinated (one dose for Janssen vaccine and two doses for the other ones) is 77.4%, the percentage of those that received at least one dose is 84.3% and those with the booster dose 56.4%. Effectiveness of the authorized vaccines has been estimated with different approaches [4,5] either for mRNA vaccines [6-10] (with a range of estimated effectiveness between 91 and 95.3%), and for the adenovirus viral vector vaccine [11][12][13] (with effectiveness between 62, 1% and 90%), even if age specific effectiveness studies [14] show that the immunity peak response is lower in elderly people than in young population [15,16]. The efficacy of the heterologous vaccine regimen has been discussed in [13] (estimated effectiveness 67% for heterologous ChAdOx1 nCoV-19 / BNT162b2 prime-boost vaccination, and 79% for heterologous ChAdOx1 nCoV-19 / mRNA-1273 prime-boost vaccination).…”

Long term effectiveness of inactivated vaccine BBIBP-CorV (Vero Cells) against COVID-19 associated severe and critical hospitalization in Morocco

“…Although studies with large national datasets do not need to calculate the minimum sample size 5 , we calculated the minimum sample size, considering that subgroup analysis will be needed to evaluate the vaccine protection effect (VE) for severe or critical infections. We estimated that VE is 80%, the population vaccination rate is approximate 50%.…”

Real-World Effectiveness of the mRNA COVID-19 Vaccines in Japan: A Case–Control Study

“…On the other hand, VE against serious illnesses requiring hospitalization was reported to still be high not only 3 months after the second vaccination but also 6 months after [ 9 , 10 , 11 , 12 , 13 , 14 ]. The degree of VE varies depending on the age and sex of the target population, underlying diseases, immune attenuation due to the time since the last vaccination, and the status of the primary epidemic strains; however, studies thoroughly examining these factors in Asian countries such as Japan remain limited [ 15 ].…”

“…However, to the best of our knowledge, no VE studies have adjusted for personal protective health behaviors and preventive measures. Most real-world studies examining VE against COVID-19 have been test-negative case–control and cohort studies using large databases to obtain information regarding vaccination, laboratory testing, clinical infection, and demographic characteristics [ 15 ]. If these databases did not include information regarding personal protective health behaviors, the VEs were not adjusted for those behaviors.…”