Comparing performance of year-round and campaign-mode influenza vaccination strategies among children aged 6-23 months in Kenya: 2019-2021.

INTRODUCTION: In 2016, the Kenya National Immunization Technical Advisory Group requested additional programmatic and cost effectiveness data to inform the choice of strategy for a national influenza vaccination program among children aged 6-23 months of age. In response, we conducted an influenza vaccine demonstration project to compare the performance of a year-round versus campaign-mode vaccination strategy. Findings from this demonstration project will help identify essential learning lessons for a national program. METHODS: We compared two vaccine delivery strategies: (i) a year-round vaccination strategy where influenza vaccines were administered throughout the year at health facilities. This strategy was implemented in Njoro sub-county in Nakuru (November 2019 to October 2021) and Jomvu sub-county in Mombasa (December 2019 to October 2021), (ii) a campaign-mode vaccination strategy where vaccines were available at health facilities over four months. This strategy was implemented in Nakuru North sub-county in Nakuru (June to September 2021) and Likoni sub-county in Mombasa (July to October 2021). We assessed differences in coverage, dropout rates, vaccine wastage, and operational needs. RESULTS: We observed similar performance between strategies in coverage of the first dose of influenza vaccine (year-round strategy 59.7 %, campaign strategy 63.2 %). The coverage obtained in the year-round sub-counties was similar (Njoro 57.4 %; Jomvu 63.1 %); however, more marked differences between campaign sub-counties were observed (Nakuru North 73.4 %; Likoni 55.2 %). The campaign-mode strategy exceeded the cold chain capacity of participating health facilities, requiring thrice monthly instead of once monthly deliveries, and was associated with a two-fold increase in workload compared to the year-round strategy (168 vaccines administered per day in the campaign strategy versus 83 vaccines administered per day in the year-round strategy). CONCLUSION: Although both strategies had similar coverage levels, the campaign-mode strategy was associated with considerable operational needs that could significantly impact the immunization program.

Knowledge and attitude of Kenyan healthcare workers towards pandemic influenza disease and vaccination: 9 years after the last influenza pandemic.

BACKGROUND: Healthcare workers (HCWs) are at high risk of exposure and transmission of infectious respiratory pathogens like influenza. Despite the potential benefits, safety and efficacy of influenza vaccination, vaccines are still underutilized in Africa, including among HCWs. METHOD: From May-June 2018, we conducted a cross-sectional, self-administered, written survey among HCWs from seven counties in Kenya and assessed their knowledge attitudes and perceptions towards pandemic influenza disease and vaccination. Using regression models, we assessed factors that were associated with the HCW's knowledge of pandemic influenza and vaccination. RESULTS: A total of 2,035 HCWs, representing 49% of the targeted respondents from 35 health facilities, completed the question. Sixty eight percent of the HCWs had ever heard of pandemic influenza, and 80.0% of these were willing to receive pandemic influenza vaccine if it was available. On average, Kenyan HCWs correctly answered 55.0% (95% CI 54.0-55.9) of the questions about pandemic influenza and vaccination. Physicians (65.6%, 95% CI 62.5-68.7) and pharmacists (61.7%, 95% CI 57.9-65.5) scored higher compared to nurses (53.1%, 95% CI 51.7-54.5). HCWs with 5 or more years of work experience (55.8, 95% CI 54.5-57.0) had marginally higher knowledge scores compared to those with less experience (53.9%, 95% CI 52.5-55.3). Most participants who were willing to receive pandemic influenza vaccine did so to protect their relatives (88.7%) or patients (85.9%). CONCLUSION: Our findings suggest moderate knowledge of pandemic influenza and vaccination by HCWs in Kenya, which varied by cadre and years of work experience. These findings highlight the need for continued in-service health education to increase the HCW's awareness and knowledge of pandemic influenza to increase acceptance of influenza vaccination in the case of a pandemic.

The Epidemiology and Burden of Influenza B/Victoria and B/Yamagata Lineages in Kenya, 2012-2016.

BACKGROUND: The impact of influenza B virus circulation in Sub-Saharan Africa is not well described. METHODS: We analyzed data from acute respiratory illness (ARI) in Kenya. We assessed clinical features and age-specific hospitalization and outpatient visit rates by person-years for influenza B/Victoria and B/Yamagata and the extent to which circulating influenza B lineages in Kenya matched the vaccine strain component of the corresponding season (based on Northern Hemisphere [October-March] and Southern Hemisphere [April-September] vaccine availability). RESULTS: From 2012 to 2016, influenza B represented 31% of all influenza-associated ARIs detected (annual range, 13-61%). Rates of influenza B hospitalization and outpatient visits were higher for <5 vs ≥5 years. Among <5 years, B/Victoria was associated with pneumonia hospitalization (64% vs 44%; P = .010) and in-hospital mortality (6% vs 0%; P = .042) compared with B/Yamagata, although the mean annual hospitalization rate for B/Victoria was comparable to that estimated for B/Yamagata. The 2 lineages co-circulated, and there were mismatches with available trivalent influenza vaccines in 2/9 seasons assessed. CONCLUSIONS: Influenza B causes substantial burden in Kenya, particularly among children aged <5 years, in whom B/Victoria may be associated with increased severity. Our findings suggest a benefit from including both lineages when considering influenza vaccination in Kenya.

The cost of influenza-associated hospitalizations and outpatient visits in Kenya.

BACKGROUND: We estimated the cost-per-episode and the annual economic burden associated with influenza in Kenya. METHODS: From July 2013-August 2014, we recruited patients with severe acute respiratory illness (SARI) or influenza-like illness (ILI) associated with laboratory-confirmed influenza from 5 health facilities. A structured questionnaire was used to collect direct costs (medications, laboratory investigations, hospital bed fees, hospital management costs, transportation) and indirect costs (productivity losses) associated with an episode of influenza. We used published incidence of laboratory-confirmed influenza associated with SARI and ILI, and the national population census data from 2014, to estimate the annual national number of influenza-associated hospitalizations and outpatient visits and calculated the annual economic burden by multiplying cases by the mean cost. RESULTS: We enrolled 275 patients (105 inpatients and 170 outpatients). The mean cost-per-episode of influenza was US$117.86 (standard deviation [SD], 88.04) among inpatients; US$114.25 (SD, 90.03) for children < 5 years, and US$137.45 (SD, 76.24) for persons aged ≥5 years. Among outpatients, the mean cost-per-episode of influenza was US$19.82 (SD, 27.29); US$21.49 (SD, 31.42) for children < 5 years, and US$16.79 (SD, 17.30) for persons aged ≥5 years. National annual influenza-associated cost estimates ranged from US$2.96-5.37 million for inpatients and US$5.96-26.35 million for outpatients. CONCLUSIONS: Our findings highlight influenza as causing substantial economic burden in Kenya. Further studies may be warranted to assess the potential benefit of targeted influenza vaccination strategies.

Influenza activity in Kenya, 2007-2013: timing, association with climatic factors, and implications for vaccination campaigns.

BACKGROUND: Information on the timing of influenza circulation remains scarce in Tropical regions of Africa. OBJECTIVES: We assessed the relationship between influenza activity and several meteorological factors (temperature, specific humidity, precipitation) and characterized the timing of influenza circulation and its implications to vaccination strategies in Kenya. METHODS: We analyzed virologically confirmed influenza data for outpatient influenza-like illness (ILI), hospitalized for severe acute respiratory infections (SARI), and cases of severe pneumonia over the period 2007-2013. Using logistic and negative binomial regression methods, we assessed the independent association between climatic variables (lagged up to 4 weeks) and influenza activity. RESULTS: There were multiple influenza epidemics occurring each year and lasting a median duration of 2-4 months. On average, there were two epidemics occurring each year in most of the regions in Kenya, with the first epidemic occurring between the months of February and March and the second one between July and November. Specific humidity was independently and negatively associated with influenza activity. Combinations of low temperature (<18°C) and low specific humidity (<11 g/kg) were significantly associated with increased influenza activity. CONCLUSIONS: Our study broadens understanding of the relationships between seasonal influenza activity and meteorological factors in the Kenyan context. While rainfall is frequently thought to be associated with influenza circulation in the tropics, the present findings suggest low humidity is more important in Kenya. If annual vaccination were a component of a vaccination strategy in Kenya, the months of April to June are proposed as optimal for associated campaigns.

Uptake and Effectiveness of a Trivalent Inactivated Influenza Vaccine in Children in Urban and Rural Kenya, 2010 to 2012.

BACKGROUND: In Africa, recent surveillance has demonstrated a high burden of influenza, but influenza vaccine is rarely used. In Kenya, a country with a tropical climate, influenza has been shown to circulate year-round, like in other tropical countries. METHODS: During 3 months in 2010 and 2011 and 2 months in 2012, the Kenya Medical Research Institute/Centers for Disease Control and Prevention-Kenya offered free injectable trivalent inactivated influenza vaccine to children 6 months to 10 years old in 2 resource-poor communities in Kenya-Kibera and Lwak (total population ~50,000). We conducted a case-control study to evaluate vaccine effectiveness (VE) in preventing laboratory-confirmed influenza associated with influenza-like illness and acute lower respiratory illness. RESULTS: Of the approximately 18,000 eligible children, 41%, 48% and 51% received at least 1 vaccine in 2010, 2011 and 2012, respectively; 30%, 36% and 38% were fully vaccinated. VE among fully vaccinated children was 57% [95% confidence interval (CI): 29% to 74%] during a 6-month follow-up period, 39% (95% CI: 17% to 56%) during a 9-month follow-up period and 48% (95% CI: 32% to 61%) during a 12-month follow-up period. For the 12-month follow-up period, VE was statistically significant in children <5 years and in children 5 to <10 years old (50% and 46%, respectively). CONCLUSIONS: In Kenya, parents of nearly half of the eligible children <10 years old chose to get their children vaccinated with a free influenza vaccine. During a 12-month follow-up period, the vaccine was moderately effective in preventing medically attended influenza-associated respiratory illness.

Results from the first six years of national sentinel surveillance for influenza in Kenya, July 2007-June 2013.

BACKGROUND: Recent studies have shown that influenza is associated with significant disease burden in many countries in the tropics, but until recently national surveillance for influenza was not conducted in most countries in Africa. METHODS: In 2007, the Kenyan Ministry of Health with technical support from the CDC-Kenya established a national sentinel surveillance system for influenza. At 11 hospitals, for every hospitalized patient with severe acute respiratory illness (SARI), and for the first three outpatients with influenza-like illness (ILI) per day, we collected both nasopharyngeal and oropharyngeal swabs. Beginning in 2008, we conducted in-hospital follow-up for SARI patients to determine outcome. Specimens were tested by real time RT-PCR for influenza A and B. Influenza A-positive specimens were subtyped for H1, H3, H5, and (beginning in May 2009) A(H1N1)pdm09. RESULTS: From July 1, 2007 through June 30, 2013, we collected specimens from 24,762 SARI and 14,013 ILI patients. For SARI and ILI case-patients, the median ages were 12 months and 16 months, respectively, and 44% and 47% were female. In all, 2,378 (9.6%) SARI cases and 2,041 (14.6%) ILI cases were positive for influenza viruses. Most influenza-associated SARI cases (58.6%) were in children <2 years old. Of all influenza-positive specimens, 78% were influenza A, 21% were influenza B, and 1% were influenza A/B coinfections. Influenza circulated in every month. In four of the six years influenza activity peaked during July-November. Of 9,419 SARI patients, 2.7% died; the median length of hospitalization was 4 days. CONCLUSIONS: During six years of surveillance in Kenya, influenza was associated with nearly 10 percent of hospitalized SARI cases and one-sixth of outpatient ILI cases. Most influenza-associated SARI and ILI cases were in children <2 years old; interventions to reduce the burden of influenza, such as vaccine, could consider young children as a priority group.

Predicting mortality among hospitalized children with respiratory illness in Western Kenya, 2009-2012.

BACKGROUND: Pediatric respiratory disease is a major cause of morbidity and mortality in the developing world. We evaluated a modified respiratory index of severity in children (mRISC) scoring system as a standard tool to identify children at greater risk of death from respiratory illness in Kenya. MATERIALS AND METHODS: We analyzed data from children <5 years old who were hospitalized with respiratory illness at Siaya District Hospital from 2009-2012. We used a multivariable logistic regression model to identify patient characteristics predictive for in-hospital mortality. Model discrimination was evaluated using the concordance statistic. Using bootstrap samples, we re-estimated the coefficients and the optimism of the model. The mRISC score for each child was developed by adding up the points assigned to each factor associated with mortality based on the coefficients in the multivariable model. RESULTS: We analyzed data from 3,581 children hospitalized with respiratory illness; including 218 (6%) who died. Low weight-for-age [adjusted odds ratio (aOR) = 2.1; 95% CI 1.3-3.2], very low weight-for-age (aOR = 3.8; 95% CI 2.7-5.4), caretaker-reported history of unconsciousness (aOR = 2.3; 95% CI 1.6-3.4), inability to drink or breastfeed (aOR = 1.8; 95% CI 1.2-2.8), chest wall in-drawing (aOR = 2.2; 95% CI 1.5-3.1), and being not fully conscious on physical exam (aOR = 8.0; 95% CI 5.1-12.6) were independently associated with mortality. The positive predictive value for mortality increased with increasing mRISC scores. CONCLUSIONS: A modified RISC scoring system based on a set of easily measurable clinical features at admission was able to identify children at greater risk of death from respiratory illness in Kenya.

Uptake and effectiveness of monovalent influenza A (H1N1) pandemic 2009 vaccine among healthcare personnel in Kenya, 2010.

INTRODUCTION: During April-June 2010, the Kenya Ministry of Public Health and Sanitation distributed free monovalent influenza A(H1N1)pdm09 vaccines to health care personnel (HCP) and other vulnerable groups. We conducted a prospective, cohort study among HCP to characterize influenza A(H1N1)pdm09 vaccine uptake, and to assess influenza A(H1N1)pdm09 vaccine effectiveness. METHODS: We enrolled HCP from 5 hospitals and followed them for 6 months. At enrollment, we asked HCP if they had received the influenza A(H1N1)pdm09 vaccine and their reasons for their decision. We administered weekly questionnaires to participants about respiratory symptoms suffered during the previous week. Participants who had acute respiratory illness were asked to contact our surveillance clinician, and nasopharyngeal and oropharyngeal specimens were collected and later tested for influenza by real-time reverse-transcriptase polymerase-chain-reaction. Vaccine effectiveness was estimated by comparing the incidence of acute respiratory illness, absenteeism from work due to respiratory illness and laboratory-confirmed influenza among vaccinated and unvaccinated HCP. RESULTS: We enrolled 3803 HCP from the five hospitals; 64% received influenza vaccine. Vaccinated HCP were more likely to develop acute respiratory illness (ARI) and more likely to report missed days of work due to respiratory illness compared to non-vaccinated HCP (adjusted incidence rate ratio (aIRR) 1.50, 95% confidence intervals (CI): 1.33-1.70) and (aIRR 2.02, 95% CI: 1.41-2.88), respectively. Of 531 samples collected from vaccinated and non-vaccinated HCP, 30 were influenza A and 3 were influenza B. Two influenza A(H1N1)pdm09 subtypes were isolated; one from vaccinated and the other from non-vaccinated HCP. DISCUSSION AND CONCLUSIONS: A majority of Kenyan HCP surveyed reported receiving the influenza A(H1N1)pdm09 vaccine. Because of low circulation of influenza A(H1N1)pdm09 virus during the study period, vaccine effectiveness could not be determined. The findings of increased ARI events and missed days of work among vaccinated HCP were likely confounded by vaccine-seeking behavioral factors.

Assessing parents' knowledge and attitudes towards seasonal influenza vaccination of children before and after a seasonal influenza vaccination effectiveness study in low-income urban and rural Kenya, 2010-2011.

BACKGROUND: Influenza vaccine is rarely used in Kenya, and little is known about attitudes towards the vaccine. From June-September 2010, free seasonal influenza vaccine was offered to children between 6 months and 10 years old in two Population-Based Infectious Disease Surveillance (PBIDS) sites. This survey assessed attitudes about influenza, uptake of the vaccine and experiences with childhood influenza vaccination. METHODS: We administered a questionnaire and held focus group discussions with parents of children of enrollment age in the two sites before and after first year of the vaccine campaign. For pre-vaccination focus group discussions, we randomly selected mothers and fathers who had an eligible child from the PBIDS database to participate. For the post-vaccination focus group discussions we stratified parents whose children were eligible for vaccination into fully vaccinated, partially vaccinated and non-vaccinated groups. RESULTS: Overall, 5284 and 5755 people completed pre and post-vaccination questionnaires, respectively, in Kibera and Lwak. From pre-vaccination questionnaire results, among parents who were planning on vaccinating their children, 2219 (77.6%) in Kibera and 1780 (89.6%) in Lwak said the main reason was to protect the children from seasonal influenza. In the pre-vaccination discussions, no parent had heard of the seasonal influenza vaccine. At the end of the vaccine campaign, of 18,652 eligible children, 5,817 (31.2%) were fully vaccinated, 2,073 (11.1%) were partially vaccinated and, 10,762 (57.7%) were not vaccinated. In focus group discussions, parents who declined vaccine were concerned about vaccine safety or believed seasonal influenza illness was not severe enough to warrant vaccination. Parents who declined the vaccine were mainly too busy [251(25%) in Kibera and 95 (10.5%) in Lwak], or their child was away during the vaccination period [199(19.8%) in Kibera; 94(10.4%) in Lwak]. CONCLUSION: If influenza vaccine were to be introduced more broadly in Kenya, effective health messaging will be needed on vaccine side effects and frequency and potential severity of influenza infection.

Hospitalized patients with pandemic (H1N1) 2009, Kenya.

To describe the epidemiology and clinical course of patients hospitalized with pandemic (H1N1) 2009 in Kenya, we reviewed medical records of 49 such patients hospitalized during July-November 2009. The median age (7 years) was lower than that in industrialized countries. More patients had HIV than the general Kenyan population.

Comparison of nasopharyngeal and oropharyngeal swabs for the diagnosis of eight respiratory viruses by real-time reverse transcription-PCR assays.

BACKGROUND: Many acute respiratory illness surveillance systems collect and test nasopharyngeal (NP) and/or oropharyngeal (OP) swab specimens, yet there are few studies assessing the relative measures of performance for NP versus OP specimens. METHODS: We collected paired NP and OP swabs separately from pediatric and adult patients with influenza-like illness or severe acute respiratory illness at two respiratory surveillance sites in Kenya. The specimens were tested for eight respiratory viruses by real-time reverse transcription-polymerase chain reaction (qRT-PCR). Positivity for a specific virus was defined as detection of viral nucleic acid in either swab. RESULTS: Of 2,331 paired NP/OP specimens, 1,402 (60.1%) were positive for at least one virus, and 393 (16.9%) were positive for more than one virus. Overall, OP swabs were significantly more sensitive than NP swabs for adenovirus (72.4% vs. 57.6%, p<0.01) and 2009 pandemic influenza A (H1N1) virus (91.2% vs. 70.4%, p<0.01). NP specimens were more sensitive for influenza B virus (83.3% vs. 61.5%, p = 0.02), parainfluenza virus 2 (85.7%, vs. 39.3%, p<0.01), and parainfluenza virus 3 (83.9% vs. 67.4%, p<0.01). The two methods did not differ significantly for human metapneumovirus, influenza A (H3N2) virus, parainfluenza virus 1, or respiratory syncytial virus. CONCLUSIONS: The sensitivities were variable among the eight viruses tested; neither specimen was consistently more effective than the other. For respiratory disease surveillance programs using qRT-PCR that aim to maximize sensitivity for a large number of viruses, collecting combined NP and OP specimens would be the most effective approach.