the importance of supplementary immunisation activities to prevent measles outbreaks CORD-Papers-2022-06-02 (Version 1)

Title: The importance of supplementary immunisation activities to prevent measles outbreaks during the COVID-19 pandemic in Kenya
Abstract: BACKGROUND: The COVID-19 pandemic has disrupted routine measles immunisation and supplementary immunisation activities (SIAs) in most countries including Kenya. We assessed the risk of measles outbreaks during the pandemic in Kenya as a case study for the African Region. METHODS: Combining measles serological data local contact patterns and vaccination coverage into a cohort model we predicted the age-adjusted population immunity in Kenya and estimated the probability of outbreaks when contact-reducing COVID-19 interventions are lifted. We considered various scenarios for reduced measles vaccination coverage from April 2020. RESULTS: In February 2020 when a scheduled SIA was postponed population immunity was close to the herd immunity threshold and the probability of a large outbreak was 34% (854). As the COVID-19 contact restrictions are nearly fully eased from December 2020 the probability of a large measles outbreak will increase to 38% (1954) 46% (3059) and 54% (4364) assuming a 15% 50% and 100% reduction in measles vaccination coverage. By December 2021 this risk increases further to 43% (2556) 54% (4363) and 67% (5972) for the same coverage scenarios respectively. However the increased risk of a measles outbreak following the lifting of all restrictions can be overcome by conducting a SIA with 95% coverage in under-fives. CONCLUSION: While contact restrictions sufficient for SAR-CoV-2 control temporarily reduce measles transmissibility and the risk of an outbreak from a measles immunity gap this risk rises rapidly once these restrictions are lifted. Implementing delayed SIAs will be critical for prevention of measles outbreaks given the roll-back of contact restrictions in Kenya. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1186/s12916-021-01906-9.
Published: 2021-02-03
Journal: BMC Med
DOI: 10.1186/s12916-021-01906-9
DOI_URL: http://doi.org/10.1186/s12916-021-01906-9
Author Name: Mburu C N
Author link: https://covid19-data.nist.gov/pid/rest/local/author/mburu_c_n
Author Name: Ojal J
Author link: https://covid19-data.nist.gov/pid/rest/local/author/ojal_j
Author Name: Chebet R
Author link: https://covid19-data.nist.gov/pid/rest/local/author/chebet_r
Author Name: Akech D
Author link: https://covid19-data.nist.gov/pid/rest/local/author/akech_d
Author Name: Karia B
Author link: https://covid19-data.nist.gov/pid/rest/local/author/karia_b
Author Name: Tuju J
Author link: https://covid19-data.nist.gov/pid/rest/local/author/tuju_j
Author Name: Sigilai A
Author link: https://covid19-data.nist.gov/pid/rest/local/author/sigilai_a
Author Name: Abbas K
Author link: https://covid19-data.nist.gov/pid/rest/local/author/abbas_k
Author Name: Jit M
Author link: https://covid19-data.nist.gov/pid/rest/local/author/jit_m
Author Name: Funk S
Author link: https://covid19-data.nist.gov/pid/rest/local/author/funk_s
Author Name: Smits G
Author link: https://covid19-data.nist.gov/pid/rest/local/author/smits_g
Author Name: van Gageldonk P G M
Author link: https://covid19-data.nist.gov/pid/rest/local/author/van_gageldonk_p_g_m
Author Name: van der Klis F R M
Author link: https://covid19-data.nist.gov/pid/rest/local/author/van_der_klis_f_r_m
Author Name: Tabu C
Author link: https://covid19-data.nist.gov/pid/rest/local/author/tabu_c
Author Name: Nokes D J
Author link: https://covid19-data.nist.gov/pid/rest/local/author/nokes_d_j
Author Name: Scott JAG
Author link: https://covid19-data.nist.gov/pid/rest/local/author/scott_jag
Author Name: Flasche S
Author link: https://covid19-data.nist.gov/pid/rest/local/author/flasche_s
Author Name: Adetifa IMO
Author link: https://covid19-data.nist.gov/pid/rest/local/author/adetifa_imo
sha: c80433def2d88db17ad594320350d224cf6f34b9
license: cc-by
license_url: https://creativecommons.org/licenses/by/4.0/
source_x: Medline; PMC
source_x_url: https://www.medline.com/https://www.ncbi.nlm.nih.gov/pubmed/
pubmed_id: 33531015
pubmed_id_url: https://www.ncbi.nlm.nih.gov/pubmed/33531015
pmcid: PMC7854026
pmcid_url: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7854026
url: https://doi.org/10.1186/s12916-021-01906-9 https://www.ncbi.nlm.nih.gov/pubmed/33531015/
has_full_text: TRUE
Keywords Extracted from Text Content: roll-back herd SAR-CoV-2 measles ≥ COVID-19 Vaccine herd infants persons measles antibodies measles U5 bold lines lockdown Measles RI [4] [5] [6] [7] age-differences participants A. Routine SARS-CoV-2 matrix contacts measles SIAs [6] [7] [8 children measles immunoglobulin G Nairobi in 2007-2009 [13 Kilifi U15 Liberia beta Sierra Leone upper Kenya's devolved counties Seventyone MCV2 C. MCV2 individuals Fig. 1 Kilifi County measles vaccine MCV2 D. vaccine-derived children ≥ 9 Rubella pre-Ebola post-COVID-19 blood samples fluorescent-bead-based COVID-19 contact restrictions measles [9 pre-COVID-19 Kilifi [18 PCVIS CIs MCV1-eligible children under-fours IgG measles [12] Fig. S1 Fig. S1 ≥ COVID-19 samples serum samples post-lockdown SF FRMvdK.CNM herd org/10.1186/s12916-021 https://doi measles IMOA DJN GS BK PGMvG Serology
Extracted Text Content in Record: First 5000 Characters:Background: The COVID-19 pandemic has disrupted routine measles immunisation and supplementary immunisation activities (SIAs) in most countries including Kenya. We assessed the risk of measles outbreaks during the pandemic in Kenya as a case study for the African Region. Methods: Combining measles serological data, local contact patterns, and vaccination coverage into a cohort model, we predicted the age-adjusted population immunity in Kenya and estimated the probability of outbreaks when contact-reducing COVID-19 interventions are lifted. We considered various scenarios for reduced measles vaccination coverage from April 2020. Results: In February 2020, when a scheduled SIA was postponed, population immunity was close to the herd immunity threshold and the probability of a large outbreak was 34% (8-54). As the COVID-19 contact restrictions are nearly fully eased, from December 2020, the probability of a large measles outbreak will increase to 38% (19-54), 46% (30-59), and 54% (43-64) assuming a 15%, 50%, and 100% reduction in measles vaccination coverage. By December 2021, this risk increases further to 43% (25-56), 54% (43-63), and 67% (59-72) for the same coverage scenarios respectively. However, the increased risk of a measles outbreak following the lifting of all restrictions can be overcome by conducting a SIA with ≥ 95% coverage in under-fives. Conclusion: While contact restrictions sufficient for SAR-CoV-2 control temporarily reduce measles transmissibility and the risk of an outbreak from a measles immunity gap, this risk rises rapidly once these restrictions are lifted. Implementing delayed SIAs will be critical for prevention of measles outbreaks given the roll-back of contact restrictions in Kenya. The SARS-CoV-2 pandemic has damaged the economy and disrupted social interaction and important health services in Kenya and elsewhere [1, 2] . The cumulative incidence of COVID-19 cases continues to rise in many parts of Africa suggesting the current mitigation measures will be maintained or reintroduced for periods at least until the pandemic peaks [3] . Despite the World Health Organization (WHO) advisory to sustain routine immunisation (RI), vaccine coverage temporarily declined in many countries including Kenya that reports a 33% disruption of RI [4] [5] [6] [7] . Following guidance from the WHO, all countries suspended scheduled measles SIAs [6] [7] [8] . Measles control in Kenya is achieved by giving children a first dose of measlescontaining vaccine (MCV1) at 9 months, and a second dose (MCV2) from 18 months. SIAs, first introduced in 2002, are conducted periodically among children < 5 years or < 15 years for accelerated control of measles [9] . Based on the accumulation of susceptible children, the timing of such campaigns has typically been chosen to close immunity gaps in time to prevent potentially large measles outbreaks. A measles SIA originally planned for 2019 was rescheduled for February 2020 due to a shortfall in funding and postponed again following the COVID-19 pandemic. Following identification of the first COVID-19 case on March 13, 2020, Kenya imposed various mitigation measures: ban on large gatherings, suspension of international flights, closure of bars, cessation of movement from hotspot counties, restriction of restaurant operating hours, and a nationwide curfew from 7 pm to 5 am. While it is plausible that these physical distancing and lock down measures may reduce the risk of measles outbreaks, they are temporary and may be associated with rebound risk periods. The availability of recent measles serological data provided the opportunity to use Kenya as a case study to estimate the impact of reduced measles vaccination coverage and suspended SIAs due to COVID-19 on the risk of measles outbreaks. This study used a cohort mathematical model that combined measles serological data, local contact patterns, and vaccination coverage estimates. We estimated measles immunity profile in children using serum samples collected during serological surveys among residents of Kilifi Health and Demographic Surveillance System (KHDSS) Kilifi, Kenya [10] for the Pneumococcal Conjugate Vaccine Impact Study (PCVIS) [11] . These serosurveys, conducted every 2 years since 2009, target 50 KHDSS randomly selected children in ten age strata (0, 1, 2, 3, 4, 5, 6, 7, (8) (9) , and 10-14 years) and blood samples < 2 ml were collected from participants. The sample size for the PCVIS serosurveys was calculated to obtain narrow confidence intervals around the estimate of prevalence of immune response both overall and by age-category for each serosurvey year. For instance, for a proportion of 0.80, the 95% confidence intervals (CIs) would be 0.77-0.84 overall and 0.69-0.91 in each age stratum. In the 2019 serosurvey, there were 497 participants and the blood samples were collected in July (165), August (162), September (130), and October (40). We tested for measles immunoglobulin G (IgG) antibodies using a
Keywords Extracted from PMC Text: pre-COVID-19 measles SIAs MCV2C.Routine MCV2D.Routine Fig. S1 matrix individuals pre-Ebola persons under-fours Nairobi in 19–54 measles [9 Kilifi County vaccine-derived measles immunoglobulin G herd serum samples measles antibodies 81–87 MCV2 vaccine measles A.Routine PCVIS Kilifi age-differences Sierra Leone blood samples − Rubella measles [12] IgG measles vaccine 40–64 Measles participants 43–63 samples 43–64 children ≥ 9 8–9 CIs ≥ sameB.Routine upper 85–91 COVID-19 contact restrictions MCV1-eligible children post-COVID-19 COVID-19 lockdown Kilifi [18 82–94 's Liberia MCV2 children SARS-CoV-2 Fig. 1 measles-containing vaccine fluorescent-bead-based 85–92 infants
Extracted PMC Text Content in Record: First 5000 Characters:The SARS-CoV-2 pandemic has damaged the economy and disrupted social interaction and important health services in Kenya and elsewhere [1, 2]. The cumulative incidence of COVID-19 cases continues to rise in many parts of Africa suggesting the current mitigation measures will be maintained or reintroduced for periods at least until the pandemic peaks [3]. Despite the World Health Organization (WHO) advisory to sustain routine immunisation (RI), vaccine coverage temporarily declined in many countries including Kenya that reports a 33% disruption of RI [4–7]. Following guidance from the WHO, all countries suspended scheduled measles SIAs [6–8]. Measles control in Kenya is achieved by giving children a first dose of measles-containing vaccine (MCV1) at 9 months, and a second dose (MCV2) from 18 months. SIAs, first introduced in 2002, are conducted periodically among children < 5 years or < 15 years for accelerated control of measles [9]. Based on the accumulation of susceptible children, the timing of such campaigns has typically been chosen to close immunity gaps in time to prevent potentially large measles outbreaks. A measles SIA originally planned for 2019 was rescheduled for February 2020 due to a shortfall in funding and postponed again following the COVID-19 pandemic. Following identification of the first COVID-19 case on March 13, 2020, Kenya imposed various mitigation measures: ban on large gatherings, suspension of international flights, closure of bars, cessation of movement from hotspot counties, restriction of restaurant operating hours, and a nationwide curfew from 7 pm to 5 am. While it is plausible that these physical distancing and lock down measures may reduce the risk of measles outbreaks, they are temporary and may be associated with rebound risk periods. The availability of recent measles serological data provided the opportunity to use Kenya as a case study to estimate the impact of reduced measles vaccination coverage and suspended SIAs due to COVID-19 on the risk of measles outbreaks. We estimated measles immunity profile in children using serum samples collected during serological surveys among residents of Kilifi Health and Demographic Surveillance System (KHDSS) Kilifi, Kenya [10] for the Pneumococcal Conjugate Vaccine Impact Study (PCVIS) [11]. These serosurveys, conducted every 2 years since 2009, target 50 KHDSS randomly selected children in ten age strata (0, 1, 2, 3, 4, 5, 6, 7, 8–9, and 10–14 years) and blood samples < 2 ml were collected from participants. The sample size for the PCVIS serosurveys was calculated to obtain narrow confidence intervals around the estimate of prevalence of immune response both overall and by age-category for each serosurvey year. For instance, for a proportion of 0.80, the 95% confidence intervals (CIs) would be 0.77–0.84 overall and 0.69–0.91 in each age stratum. In the 2019 serosurvey, there were 497 participants and the blood samples were collected in July (165), August (162), September (130), and October (40). We tested for measles immunoglobulin G (IgG) antibodies using a fluorescent-bead-based multiplex immunoassay. Antibody concentrations ≥ 0.12 IU/ml were considered protective against measles [12]. We assumed these results reflected measles immunity in Kilifi in August 2019 and assumed 96% of persons > 15 years had protective measles antibodies concentrations, similar to findings in adults in Nairobi in 2007–2009 [13] (Table 1). We also assumed protection from maternal immunity was similar to the proportions of the infants < 9 months old who had protective antibodies. MCV1 national coverage in Kenya has been between 75 and 80% since its introduction in 1985 [17]. MCV2 was introduced in Kenya in 2013 and coverage rose up to 45% in 2018 [9]. The last measles SIA in children aged 9 months to 14 years took place in 2016 and achieved 95% coverage [22]. We assumed national MCV1 and MCV2 coverage were 79% and 45%, respectively, in 2018, and that these stayed at the same level from August 2019 until the end of March 2020 when COVID-19 contact restrictions were introduced in Kenya. From April 2020, we explored the following routine vaccination coverage scenarios alongside a suspended SIA. A.Routine vaccination coverage remained the sameB.Routine vaccination coverage reduced by 15% for both MCV1 and MCV2C.Routine vaccination coverage reduced by 50% for both MCV1 and MCV2D.Routine vaccination was suspended We used an age-mixing matrix which consisted of the number of contacts between six different age groups. The matrix was generated from diary studies conducted in Kilifi, Kenya [21], using a bootstrap of 4000 samples by randomly sampling n individuals with replacement from the n participants of the contact survey. We adapted a static cohort model of measles immunity [23] to estimate age-stratified population immunity profile in Kilifi by combining recent measles serological data with new vaccine-derived immunity during the prediction period using the
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