Assessing the impact of COVID-19 on routine immunization in Sierra Leone

Abstract

Background: The COVID-19 pandemic had a profound impact on healthcare systems and services, including routine immunization (RI). To date, there is limited information on the effects of the COVID-19 pandemic on RI in West African countries such as Sierra Leone, which had already experienced public health emergencies that disrupted its healthcare system. Here, we describe the impact of the COVID-19 pandemic on the RI of key antigens in Sierra Leone.

Methods: We used vaccination data from the District Health Information System for BCG, measles-rubella 1 and 2, and pentavalent 1 and 3 antigens. We compared 2019, 2020, 2021, and 2022 annual coverage rates for the selected antigens at the national and district levels. We used the Pearson chi-square test to assess the difference between annual coverage rates between 2019 and 2020, 2020-2021, and 2021-2022.

Results: National coverage rates for all antigens declined in 2019-2020, notably measles-rubella 1 and pentavalent 3 (-5.4% and - 4.9%). Between 2020 and 2021, there was an overall increase in coverage (+ 0.2% to + 2.5%), except for measles-rubella 2 (-1.8%). Measles-rubella antigens rebounded in 2021-2022, while others decreased between - 0.5 and - 1.9% in coverage. Overall, all district-level coverage rates in 2022 were lower than those in 2019. Most districts decreased between 2019 and 2022, though a few had a continuous increase; some had an increase/recovery between 2020 and 2021; some districts had recovered 2019 levels by 2022.

Conclusion: The COVID-19 pandemic impacted Sierra Leone's national BCG, measles-rubella, and pentavalent antigen immunization, which were not fully restored in 2022. Most districts experienced notable coverage declines during the pandemic, though a few reached or surpassed 2019 rates in 2022. Examining pandemic impact can benefit from a focus beyond the national level to identify vulnerable regions. Sierra Leone's post-pandemic RI reestablishment needs targeted strategies and continual investments for equitable access and coverage, as well as to prevent vaccine-preventable diseases.

Keywords: BCG vaccine; Bacillus calmette–guérin; COVID-19; Health Information system; Measles-Rubella; Pandemic; Pentavalent vaccine; Public health emergencies; Routine immunization; Sierra leone; Vaccination coverage rate.

Fig. 1

Changes in annual coverage rates at the national level. Each panel presents the change comparison between the focus years: (a) 2019–2020, (b) 2020–2021, and (c) 2021–2022. The difference between each comparison is presented on the right-hand side of the plot. Red lines and values represent a decrease in annual coverage; blue means an increase. All values are in percentage points of the annual coverage rate (%)

Fig. 2

BCG mean annual coverage rates between 2019 and 2022 in Sierra Leone’s districts. Each panel presents the mean annual coverage rates of all districts: the focus district is presented in colour, and all others in grey. Red points and lines sign signify that the 2022 coverage rate is below the 2019 value; blue is the opposite. Some coverages exceeded 100% because the vaccination doses administered exceeded the target population projected for that district for that year

Fig. 3

Measles-rubella 1 mean annual coverage rates between 2019 and 2022 in Sierra Leone’s districts. Each panel presents the mean annual coverage rates of all districts: the focus district is presented in colour, and all others in grey. Red points and lines signify that the 2022 coverage rate is below the 2019 value; blue is the opposite. Some coverages exceeded 100% because the vaccination doses administered exceeded the target population projected for that district for that year

Fig. 4

Pentavalent 1 mean annual coverage rates between 2019 and 2022 in Sierra Leone’s districts. Each panel presents the mean annual coverage rates of all districts: the focus district is presented in colour, and all others in grey. Red points and lines signify that the 2022 coverage rate is below the 2019 value; blue is the opposite. Some coverages exceeded 100% because the vaccination doses administered exceeded the target population projected for that district for that year