COVID-19 Vaccine Safety Monitoring Studies in Low- and Middle-Income Countries (LMICs)-A Systematic Review of Study Designs and Methods

Landscape review of active vaccine safety surveillance activities for COVID-19 vaccines globally

Background

Evidence of COVID-19 vaccine safety relied upon the global vaccine monitoring infrastructure due to shortened clinical development timelines and emergency use licensure. Differences in AVSS capacity between high-income countries (HICs) versus low- and middle-income countries (LMICs) were known prior to the pandemic.

Objective

To assess the global landscape of COVID-19 vaccine AVSS activities to identify gaps in safety evidence generation across vaccine products and populations with a focus on LMICs.

Methods

A cross-sectional survey was conducted in January 2022 on AVSS activities evaluating adverse events following immunization (AEFI). Data collected included country, targeted population, COVID-19 vaccine product(s), design of surveillance/monitoring activities or study, and AEFIs to be monitored.To supplement these findings, we conducted a literature review of COVID-19 vaccine safety activities published in PubMed through January 2023. Observational activities assessing AEFI, specifically adverse events of special interest (AESI), following routine use of COVID-19 vaccines in medical practice were included; systematic reviews, benefit/risk assessments, clinical trials, and case reports/series were excluded.

Results

The survey, completed by 34 respondents and compiled with reviews of 7 publicly available Risk Management Plans from five vaccine manufacturers, identified 79 monitoring activities in HICs, 24 in LMICs, and 9 in multiple regions. Most activities in LMICs were planned cohort event monitoring (CEM) studies (n = 18); two multi-national hospital-based sentinel surveillance studies for AESI were ongoing. Activities in LMICs evaluated multiple COVID-19 vaccine products simultaneously and were sponsored by health authorities. The literature review identified 1245 unique citations, of which 379 met inclusion criteria. The majority evaluated vaccines primarily used in high-income countries: Pfizer BioNTech (Comirnaty; n = 303), Moderna (mRNA-1273; n = 164), AstraZeneca (AZD1222; n = 126), and Janssen (Ad26.COV2.S); n = 62); 14 citations assessed vaccines used exclusively in LMICs: Sinovac (CoronaVac), Beijing CNBG (BBIBP-Corv), Bharat (Covaxin), SII (Covashield), and Gamaleya (Gam-Covid-Vac) vaccines.

Conclusions

Robust safety evidence for input into benefit/risk assessments is likely unavailable for most COVID-19 vaccines used primarily in LMICs due to emphasis on cohort event monitoring methods. Goals for equitable vaccine access should be coupled with investment and support for building infrastructure and capacity for safety evidence generation to inform policy and regulatory decisions at local levels.

Importance of Examining Incidentality in Vaccine Safety Assessment

The author believes that the principles of statistical methods for vaccine safety can be divided into three categories: comparison of adverse event incidence rates between vaccinated and unvaccinated groups, analysis of incidentality in the vaccinated group, and a combination of both. The first category includes the cohort study; the second, the self-controlled risk interval design (SCRI); and the third, the self-controlled case series method. A single p-value alone should not determine a scientific conclusion, and analysis should be performed using multiple statistical methods with different principles. The author believes that using both the cohort study and the SCRI for analysis is the best method to assess vaccine safety. When the cohort study may not detect a significant difference owing to a low incidence rate of an adverse event in the vaccinated group or a high one in the unvaccinated group, the SCRI may detect it. Because vaccines must have a higher level of safety than the pharmaceuticals used for treatment, vaccine safety is advisable to be assessed using methods that can detect a significant difference even for any value of the incidence rate of an adverse event. The author believes that the analyses of COVID-19 vaccine safety have areas for improvement because the proportion of papers that used the cohort study and the SCRI was negligible.

Serosurveillance among urban slum and non-slum populations immunized with COVID-19 vaccines in Bangladesh

Using two rounds of serosurveillance, we aimed to observe the COVID-19 vaccination status and the dynamics of antibody responses to different vaccines among urban slum and non-slum populations of Bangladesh. Adults (>18 years) and children (10-17 years) were enrolled in March and October 2022. Data including COVID-19 vaccine types and dosage uptake were collected. SARS-CoV-2 spike (S)-specific antibodies were measured in blood. The proportion of vaccinated children was significantly lower among slum than non-slum populations. Two doses of vaccines showed an increase in the level of anti-S-antibodies up to 2 months, followed by reduced levels at 2-6 months and a resurgence at 6-12 months. Children showed significantly higher anti-S-antibodies after two doses of the Pfizer-BioNTech vaccine than adults; however, after 6 months, the level of antibodies declined in younger children (10 - < 12 years). In a mixed vaccine approach, mRNA vaccines contributed to the highest antibody response whether given as the first two doses or as the third dose. Our findings emphasized the need for increasing the coverage of COVID-19 vaccination among slum children and booster dosing among all children. The use of mRNA vaccines in the mixed vaccination approach was found to be useful in boosting the antibody response to SARS-CoV-2.