Predicting the impact of household contact and mass chemoprophylaxis on future new leprosy cases in South Tarawa, Kiribati: A modelling study

BACKGROUND: The country of Kiribati is a small Pacific island nation which had a new case detection rate of 191 per 100,000 in 2016, and is one of the few countries yet to reach the WHO leprosy elimination goal. Chemoprophylaxis of household contacts of new cases, or to the whole population in a highly endemic areas have been found to be effective in reducing new case rates. This study investigated the potential impact of different chemoprophylaxis strategies on future cases in South Tarawa, the main population centre of Kiribati. METHODOLOGY: The microsimulation model SIMCOLEP was calibrated to simulate the South Tarawa population and past leprosy control activities, and replicate annual new cases from 1989 to 2016. The impact of six different strategies for delivering one round of single dose rifampicin (SDR) chemoprophylaxis to household contacts of new cases and/or one or three rounds of SDR to the whole population was modelled from 2017 to 2030. PRINCIPAL FINDINGS: Our model predicted that continuing the existing control program of high levels of public awareness, passive case detection, and treatment with multidrug treatment would lead to a substantial reduction in cases but this was less effective than all modelled intervention scenarios. Mass chemoprophylaxis led to a faster initial decline in cases than household contact chemoprophylaxis alone, however the decline under the latter was sustained for longer. The greatest cumulative impact was for household contact chemoprophylaxis with three rounds of mass chemoprophylaxis at one-year intervals. CONCLUSIONS: The results suggest that control of leprosy would be achieved most rapidly with a combination of intensive population-based and household chemoprophylaxis. These findings may be generalisable to other countries where crowding places social contacts as well as household contacts of cases at risk of developing leprosy

Changes in Invasive Pneumococcal Disease Caused by Streptococcus pneumoniae Serotype 1 following Introduction of PCV10 and PCV13: Findings from the PSERENADE Project

Streptococcus pneumoniae serotype 1 (ST1) was an important cause of invasive pneumococcal disease (IPD) globally before the introduction of pneumococcal conjugate vaccines (PCVs) containing ST1 antigen. The Pneumococcal Serotype Replacement and Distribution Estimation (PSERENADE) project gathered ST1 IPD surveillance data from sites globally and aimed to estimate PCV10/13 impact on ST1 IPD incidence. We estimated ST1 IPD incidence rate ratios (IRRs) comparing the pre-PCV10/13 period to each post-PCV10/13 year by site using a Bayesian multi-level, mixed-effects Poisson regression and all-site IRRs using a linear mixed-effects regression (N = 45 sites). Following PCV10/13 introduction, the incidence rate (IR) of ST1 IPD declined among all ages. After six years of PCV10/13 use, the all-site IRR was 0.05 (95% credibility interval 0.04-0.06) for all ages, 0.05 (0.04-0.05) for <5 years of age, 0.08 (0.06-0.09) for 5-17 years, 0.06 (0.05-0.08) for 18-49 years, 0.06 (0.05-0.07) for 50-64 years, and 0.05 (0.04-0.06) for ≥65 years. PCV10/13 use in infant immunization programs was followed by a 95% reduction in ST1 IPD in all ages after approximately 6 years. Limited data availability from the highest ST1 disease burden countries using a 3+0 schedule constrains generalizability and data from these settings are needed

Predicting the impact of chemoprophylaxis strategies against leprosy in South Tarawa, Kiribati

Background Leprosy is widely thought to be a disease of the past, but globally there are still around 200,000 new cases annually. Current strategies of early diagnosis and treatment are proving ineffective in interrupting transmission. Providing targeted chemoprophylaxis to household contacts of confirmed cases or to the general population are proving to be promising new control strategies. Kiribati, a small island nation of around 110,000 people, is one of the few countries yet to reach the WHO leprosy elimination goal of a prevalence of less than one case per 10,000 population. In order to accelerate the interruption of transmission the Kiribati Ministry of Health plans to implement chemoprophylaxis in its capital, South Tarawa. This research aimed to determine the most effective chemoprophylaxis intervention strategy for South Tarawa. Methods The existing leprosy transmission model SIMCOLEP was quantified to simulate the population and the number of new leprosy cases in South Tarawa from 1989 to 2016. Quantification involved the assembly of data, parameterisation of the model, and the calibration of unknown demographic and disease parameters. Seven chemoprophylaxis interventions were simulated from 2017 to 2030 to predict the impact of adding chemoprophylaxis interventions to the current leprosy control strategy; household contact only, one round of mass, three rounds of mass, one round of mass with household contact, three rounds of mass (in consecutive years, every two years, and every five years) with household contact. These were all simulated at 100% and 80% adherence of individuals. Results The model predicted that the number of future leprosy cases would significantly decrease under the current control strategy alone, but that all interventions are expected to lead to faster and greater declines. Mass chemoprophylaxis leads to faster initial declines in cases than household contact only, with additional reductions with an increasing number of rounds. A combined strategy of three rounds of mass chemoprophylaxis implemented in consecutive years and household contact chemoprophylaxis is predicted to be the most effective approach because it results in the greatest reduction in cumulative cases over the prediction period. Lower adherence of individuals is predicted to reduce the speed and magnitude of the additional reductions for all interventions, however it does not impact on their relative effectiveness. Conclusion This model showed that all chemoprophylaxis interventions would be beneficial for reducing new leprosy cases in South Tarawa in the future. The most effective approach for interrupting transmission in Kiribati would be three rounds of mass chemoprophylaxis implemented in consecutive years, with ongoing household contact chemoprophylaxis. Decisions must also be aided by considerations of operational feasibility and cost-effectiveness

Predicting the impact of chemoprophylaxis strategies against leprosy in South Tarawa, Kiribati

Background Leprosy is widely thought to be a disease of the past, but globally there are still around 200,000 new cases annually. Current strategies of early diagnosis and treatment are proving ineffective in interrupting transmission. Providing targeted chemoprophylaxis to household contacts of confirmed cases or to the general population are proving to be promising new control strategies. Kiribati, a small island nation of around 110,000 people, is one of the few countries yet to reach the WHO leprosy elimination goal of a prevalence of less than one case per 10,000 population. In order to accelerate the interruption of transmission the Kiribati Ministry of Health plans to implement chemoprophylaxis in its capital, South Tarawa. This research aimed to determine the most effective chemoprophylaxis intervention strategy for South Tarawa. Methods The existing leprosy transmission model SIMCOLEP was quantified to simulate the population and the number of new leprosy cases in South Tarawa from 1989 to 2016. Quantification involved the assembly of data, parameterisation of the model, and the calibration of unknown demographic and disease parameters. Seven chemoprophylaxis interventions were simulated from 2017 to 2030 to predict the impact of adding chemoprophylaxis interventions to the current leprosy control strategy; household contact only, one round of mass, three rounds of mass, one round of mass with household contact, three rounds of mass (in consecutive years, every two years, and every five years) with household contact. These were all simulated at 100% and 80% adherence of individuals. Results The model predicted that the number of future leprosy cases would significantly decrease under the current control strategy alone, but that all interventions are expected to lead to faster and greater declines. Mass chemoprophylaxis leads to faster initial declines in cases than household contact only, with additional reductions with an increasing number of rounds. A combined strategy of three rounds of mass chemoprophylaxis implemented in consecutive years and household contact chemoprophylaxis is predicted to be the most effective approach because it results in the greatest reduction in cumulative cases over the prediction period. Lower adherence of individuals is predicted to reduce the speed and magnitude of the additional reductions for all interventions, however it does not impact on their relative effectiveness. Conclusion This model showed that all chemoprophylaxis interventions would be beneficial for reducing new leprosy cases in South Tarawa in the future. The most effective approach for interrupting transmission in Kiribati would be three rounds of mass chemoprophylaxis implemented in consecutive years, with ongoing household contact chemoprophylaxis. Decisions must also be aided by considerations of operational feasibility and cost-effectiveness

The impact of pneumococcal serotype replacement on the effectiveness of a national immunization program: a population-based active surveillance cohort study in New&nbsp;Zealand.

BACKGROUND: In Aotearoa New Zealand (NZ) PCV7 was introduced in 2008, then PCV10 in 2011 and PCV13 in 2014. In 2017 PCV10 was re-introduced, replacing PCV13. In the present study, we investigate the resultant rapidly changing invasive pneumococcal disease (IPD) epidemiology. METHODS: We compare the IPD incidence rate ratio (IRR) in NZ (2022 versus 2020) with other countries, and describe the IPD epidemiology (including trends in overall IPD and serotype 19A, and antimicrobial resistance) within NZ. Additionally, we performed a genomic-epidemiology investigation identifying the most common 19A sequence types and associated risk factors. FINDINGS: Though IPD incidence rates have increased in the US and Australia (2021-22) after declines in 2020, in NZ the incidence rate is the highest since 2011 with a significantly higher IRR than US (p&nbsp;&lt;&nbsp;0.01). Incidence rates among children &lt;2 and adults 65 or over in 2022 are the highest since 2009, driven by significant increases of serotype 19A (p&nbsp;=&nbsp;0.01). Māori and Pacific peoples are experiencing the highest rates since 2009. Further, penicillin resistance among 19A isolates has increased from 39% (2012) to 84% (2021) (p&nbsp;=&nbsp;0.02). Genomic sequencing identified the more virulent ST-2062 as most common among 19A isolates sequenced, increasing from 5% (2010) to 55% (2022). INTERPRETATION: With very high incidence rates of IPD in NZ, inadequate protection against 19A, increasing resistance, and a more virulent 19A clade, targeted public health campaigns and increased PCV13 availability are needed. FUNDING: The NZ Ministry of Health funds IPD surveillance and typing in NZ