Epidemiology of measles cases, vaccine effectiveness, and performance towards measles elimination in The Gambia

Abstract

Introduction In 2011, member states of the World Health Organization (WHO) Africa Regional Office (AFRO) resolved to eliminate Measles by 2020. Our study aims to assess The Gambia’s progress towards the set AFRO measles elimination target and highlight surveillance and immunisation gaps to better inform future measles prevention strategies. Material and methods A retrospective review of measles surveillance data for the period 2011–2019, was extracted from The Gambia case-based measles surveillance database. WHO—UNICEF national coverage estimates were used for estimating national level MCV coverage. Measles post campaign coverage survey coverage estimates were used to estimate national measles campaign coverage. Results One hundred and twenty-five of the 863 reported suspected cases were laboratory confirmed as measles cases. More than half (53.6%) of the confirmed cases have unknown vaccination status, 24% of cases were vaccinated, 52.8% of cases occurred among males, and 72.8% cases were among urban residents. The incidence of measles cases per million population was lowest (0) in 2011–2012 and highest in 2015 and 2016 (31 and 23 respectively). The indicator for surveillance sensitivity was met in all years except in 2016 and 2019. Children aged 5–9 years (Incidence Rate Ratio—IRR = 0.6) and residents of Central River region (IRR = 0.21) had lower measles risk whilst unvaccinated (Adjusted IRR = 5.95) and those with unknown vaccination status (IRR 2.21) had higher measles risk. Vaccine effectiveness was 89.5%. Conclusion The Gambia’s quest to attain measles elimination status by 2020 has registered significant success but it is unlikely that all target indicators will be met. Vaccination has been very effective in preventing cases. There is variation in measles risk by health region, and it will be important to take it into account when designing prevention and control strategies. The quality of case investigations should be improved to enhance the quality of surveillance for decision making.

Epidemiology of confirmed measles virus cases, surveillance, incidence, and associated factors in Eritrea: 18-year retrospective analysis

“…Similar to other studies in the region (32), we observed a signi cant geographical variation in the likelihood of test positivity. Predictably, the likelihood of test positivity was lower in Maekel; the zone where testing is concentrated and vaccine coverage is higher.…”

“…Separately, we found a connection between measles test positivity and vaccination. This outcome is supported by previous studies done in Ethiopia (18,34), South Sudan (35), and Gambia (32). Interestingly, individuals who were vaccinated before 2010 had a higher likelihood of measles test positivity.…”

Measles: Global Indicators and Progress on the road for Achieving and Sustaining Virus Eradication: A Review

“…By 2008 all WHO member nations (193) offered one dose of MCV1 (measles vaccine) although the timing of schedules varied, 132 countries offered MCV2 as part of the routine schedule and 152 countries conducted SIAs with the result that 192 countries provided a 2 nd shot of MCV either as a regular second jab, or SIAs or mutually. By 2010, all member countries offered MCV2, with 139 countries offering it as part of the routine schedule (CDC, 2012) (8,(31)(32)(33)(34). The level of vaccine coverage varies greatly between countries and in 2009 the average global measles vaccination coverage was only 82%, and increased from 58% in 2000 to 78% in 2010 in the 47 priority countries (CDC, 2012).…”

“…The MI is an international organization founded and led by the World Health Organization (WHO), United Nations International Children's Emergency Fund (UNICEF), Centers for Disease Control and Prevention (CDC) and American Red Cross. However, due to global financial constraints, financial assistance to the Measles Initiative reduced from US$ 150M in 2009 to US$ 35M in 2010, (33,(37)(38)(39) and a number of prioritized states have been unable to generate the required 50% of the operating costs, resulting in the delay of scheduled SIAs and drops in the range of targeted age groups. It is estimated that the progress in measles fatality reduction will be lost unless the financial situation can be improved, and indeed, a reappearance of measles has been observed influencing 28 counties in sub-Saharan Africa from the latter part of 2009 resulting in more than 200, 000 recorded cases as well as more than 1400 recorded fatalities but as there is under-reporting of both cases and deaths, it is estimated that the figures are likely to be 10-20 fold higher.…”

Evaluation of Measles Surveillance System, Bono Region, Ghana

“…It is meant to reduce morbidity and mortality and improve measles vaccination coverage to eliminate the disease in the country. The measles vaccine is one of the best investments in public health as it saved 23.2 million lives between 2000 and 2018 [5,6]. However, measles disease surveillance is a critical component of measles control and elimination efforts and is used in the assessment of progress and in making adjustments to programmes as required [7].…”