Estimating the household secondary attack rate with the Incomplete Chain Binomial model

The Secondary Attack Rate (SAR) is a measure of how infectious a communicable disease is, and is often estimated based on studies of disease transmission in households. The Chain Binomial model is a simple model for disease outbreaks, and the final size distribution derived from it can be used to estimate the SAR using simple summary statistics. The final size distribution of the Chain Binomial model assume that the outbreaks have concluded, which in some instances may require long follow-up time. We develop a way to compute the probability distribution of the number of infected before the outbreak has concluded, which we call the Incomplete Chain Binomial distribution. We study a few theoretical properties of the model. We develop Maximum Likelihood estimation routines for inference on the SAR and explore the model by analyzing two real world data sets.Comment: 16 page

Cost-effectiveness of meningococcal vaccination of Norwegian teenagers with a quadrivalent ACWY conjugate vaccine

n Norway, the incidence of invasive meningococcal disease (IMD) is higher among 16–19-year-olds than in the general population. Most IMD cases among teenagers are caused by serogroup Y. Since 2011, one dose of meningococcal ACWY conjugate vaccine (MCV4) has been recommended for teenagers with out- of-pocket payment. The teenagers are usually vaccinated through the school health service at age 18. This study aimed to estimate costs and health gains of introducing MCV4 to Norwegian teenagers through the national immunization program (NIP). A Markov model was used to analyze the cost-effectiveness of universal MCV4 vaccination of either 15-year-olds or 18-years-olds. Occurrences of IMD were simulated from 15 until 23 years of age. Costs were estimated from a healthcare perspective. Sensitivity analyses evaluated the impact of vaccine price, vaccination uptake, IMD incidence and discount rate. Compared to today’s practice of vaccinating 18-year-olds with out-of-pocket payment, introducing MCV4 to 15-year- olds in a NIP-setting, with 90% vaccine uptake and 50% rebate on vaccine price, prevented 3.2 hospita-lizations, 0.20 sequelae and 0.47 deaths among 15–23-year-olds, annually. Total costs were reduced by €30,000 and 9.7 quality-adjusted life-years (QALYs) were gained per birth cohort. The probability of cost- effectiveness was 99.0%, assuming a willingness-to-pay threshold of €86,000/QALY for severe diseases in Norway. Cost-effectiveness was highly dependent on vaccine price. Vaccination of 18-year-olds in a NIP- setting was also cost-effective, but less than NIP-vaccination of 15-year-olds. Introduction of MCV4 to the 15-year-olds in the Norwegian NIP is likely to be cost-effective given a rebate on the vaccine price

Cost-effectiveness of meningococcal vaccination of Norwegian teenagers with a quadrivalent ACWY conjugate vaccine

n Norway, the incidence of invasive meningococcal disease (IMD) is higher among 16–19-year-olds than in the general population. Most IMD cases among teenagers are caused by serogroup Y. Since 2011, one dose of meningococcal ACWY conjugate vaccine (MCV4) has been recommended for teenagers with out- of-pocket payment. The teenagers are usually vaccinated through the school health service at age 18. This study aimed to estimate costs and health gains of introducing MCV4 to Norwegian teenagers through the national immunization program (NIP). A Markov model was used to analyze the cost-effectiveness of universal MCV4 vaccination of either 15-year-olds or 18-years-olds. Occurrences of IMD were simulated from 15 until 23 years of age. Costs were estimated from a healthcare perspective. Sensitivity analyses evaluated the impact of vaccine price, vaccination uptake, IMD incidence and discount rate. Compared to today’s practice of vaccinating 18-year-olds with out-of-pocket payment, introducing MCV4 to 15-year- olds in a NIP-setting, with 90% vaccine uptake and 50% rebate on vaccine price, prevented 3.2 hospita-lizations, 0.20 sequelae and 0.47 deaths among 15–23-year-olds, annually. Total costs were reduced by €30,000 and 9.7 quality-adjusted life-years (QALYs) were gained per birth cohort. The probability of cost- effectiveness was 99.0%, assuming a willingness-to-pay threshold of €86,000/QALY for severe diseases in Norway. Cost-effectiveness was highly dependent on vaccine price. Vaccination of 18-year-olds in a NIP- setting was also cost-effective, but less than NIP-vaccination of 15-year-olds. Introduction of MCV4 to the 15-year-olds in the Norwegian NIP is likely to be cost-effective given a rebate on the vaccine price

Meningococcal carriage in Norwegian teenagers: strain characterisation and assessment of risk factors

Abstract Teenagers have a higher risk of invasive meningococcal disease (IMD) than the general population. This cross-sectional study aimed to characterise strains of Neisseria meningitidis circulating among Norwegian teenagers and to assess risk factors for meningococcal carriage. Oropharyngeal swabs were collected from secondary-school students in southeastern Norway in 2018–2019. Meningococcal isolates were characterised using whole genome sequencing. Risk factors for meningococcal carriage were assessed from questionnaire data. Samples were obtained from 2296 12–24-year-olds (majority 13–19-year-olds). N. meningitidis was identified in 167 (7.3%) individuals. The highest carriage rate was found among 18-year-olds (16.4%). Most carriage isolates were capsule null (40.1%) or genogroup Y (33.5%). Clonal complexes cc23 (35.9%) and cc198 (32.3%) dominated and 38.9% of carriage strains were similar to invasive strains currently causing IMD in Norway. Use of Swedish snus (smokeless tobacco) (OR 1.56, 95% CI 1.07–2.27), kissing >two persons/month (OR 2.76, 95% CI 1.49–5.10) and partying >10 times/3months (OR 3.50, 95% CI 1.45–8.48) were associated with carriage, while age, cigarette smoking, sharing of drinking bottles and meningococcal vaccination were not. The high meningococcal carriage rate among 18-year-olds is probably due to risk-related behaviour. Use of Swedish snus is possibly a new risk factor for meningococcal carriage. Almost 40% of circulating carriage strains have invasive potential

Meningococcal carriage in Norwegian teenagers: strain characterisation and assessment of risk factors

Abstract Teenagers have a higher risk of invasive meningococcal disease (IMD) than the general population. This cross-sectional study aimed to characterise strains of Neisseria meningitidis circulating among Norwegian teenagers and to assess risk factors for meningococcal carriage. Oropharyngeal swabs were collected from secondary-school students in southeastern Norway in 2018–2019. Meningococcal isolates were characterised using whole genome sequencing. Risk factors for meningococcal carriage were assessed from questionnaire data. Samples were obtained from 2296 12–24-year-olds (majority 13–19-year-olds). N. meningitidis was identified in 167 (7.3%) individuals. The highest carriage rate was found among 18-year-olds (16.4%). Most carriage isolates were capsule null (40.1%) or genogroup Y (33.5%). Clonal complexes cc23 (35.9%) and cc198 (32.3%) dominated and 38.9% of carriage strains were similar to invasive strains currently causing IMD in Norway. Use of Swedish snus (smokeless tobacco) (OR 1.56, 95% CI 1.07–2.27), kissing >two persons/month (OR 2.76, 95% CI 1.49–5.10) and partying >10 times/3months (OR 3.50, 95% CI 1.45–8.48) were associated with carriage, while age, cigarette smoking, sharing of drinking bottles and meningococcal vaccination were not. The high meningococcal carriage rate among 18-year-olds is probably due to risk-related behaviour. Use of Swedish snus is possibly a new risk factor for meningococcal carriage. Almost 40% of circulating carriage strains have invasive potential

Antibody levels in a cohort of pregnant women after the 2009 influenza A(H1N1) pandemic: Waning and association with self-reported severity and duration of illness

publishedVersio

Salivary and serum antibody response against Neisseria meningitidis after vaccination with conjugate polysaccharide vaccines in Ethiopian volunteers

Meningococcal conjugate vaccines induce serum antibodies crucial for protection against invasive disease. Salivary antibodies are believed to be important for hindering meningococcal acquisition and/or clearance of established carriage. In this study, we measured salivary IgA and IgG antibodies induced by vaccination with a monovalent serogroup A conjugate vaccine or a tetravalent A, C, W and Y conjugate vaccine, in comparison with antibody levels in serum. Saliva and serum samples from Ethiopian volunteers (1–29 years) collected before and eight times on a weekly basis after receiving the serogroup A conjugate vaccine, the tetravalent serogroup A, C, W and Y conjugate vaccine, or no vaccine (control group), were analysed using a multiplex microsphere immunoassay for antibody detection. Serogroup-specific IgG antibody levels in saliva increased significantly after vaccination with both vaccines. The monovalent serogroup A vaccine also induced an increase in salivary IgA antibodies. A strong correlation between serogroup-specific IgG antibodies in saliva and serum, and a somewhat lower correlation for IgA, was observed for all serogroups. There was also a strong correlation between specific secretory IgA and IgA antibodies in saliva for all serogroups. Meningococcal conjugate vaccines are able to elicit salivary antibodies against serogroup A, C, W and Y correlating with antibody levels in serum. The strong correlation between saliva and serum antibody levels indicates that saliva may be used as a surrogate of systemic antibody responses