An evaluation of an influenza vaccination campaign targeting pregnant women in 27 clinics in two provinces of South Africa, 2015 - 2018

Introduction

Despite prioritization, routine antenatal influenza vaccine coverage is < 16% in South Africa. We aimed to describe maternal influenza vaccine coverage in 27 antenatal clinics (ANCs) in Gauteng and Western Cape (WC) Provinces, where in collaboration with the Department of Health (DoH), we augmented the annual influenza vaccination programme among pregnant women.

Methods

From 2015 through 2018, 40,230 additional doses of influenza vaccine were added to the available stock and administered as part of routine antenatal care. Educational talks were given daily and data were collected on women attending ANCs. We compared characteristics of vaccinated and unvaccinated women using multivariable logistic regression.

Results

We screened 62,979 pregnant women during the period when Southern Hemisphere influenza vaccines were available (27,068 in Gauteng and 35,911 in WC). Vaccine coverage at the targeted clinics was 78.7% (49,355/62682), although pregnant women in WC were more likely to be vaccinated compared to those in the Gauteng (Odds ratio (OR) =3.7 p < 0.001). Women aged 25—29 and > 35 years were less likely to be vaccinated than women aged 18—24 years (OR = 0.9 p = 0.053; OR = 0.9 p < 0.001). HIV positive status was not associated with vaccination (OR = 1.0 p = 0.266). Reasons for not vaccinating included: vaccine stock-outs where ANCs depleted available stock of vaccines and/or were awaiting delivery of vaccines (54.6%, 6949/12723), refusal/indecision (25.8%, 3285), and current illness that contraindicated vaccination (19.6%, 2489).

Conclusion

Antenatal vaccination uptake was likely improved by the increased vaccine supply and vaccine education offered during our campaign.

Decline of influenza and respiratory syncytial virus detection in facility-based surveillance during the COVID-19 pandemic, South Africa, January to October 2020

Background

In South Africa, COVID-19 control measures to prevent SARS-CoV-2 spread were initiated on 16 March 2020. Such measures may also impact the spread of other pathogens, including influenza virus and respiratory syncytial virus (RSV) with implications for future annual epidemics and expectations for the subsequent northern hemisphere winter.

Methods

We assessed the detection of influenza and RSV through facility-based syndromic surveillance of adults and children with mild or severe respiratory illness in South Africa from January to October 2020, and compared this with surveillance data from 2013 to 2019.

Results

Facility-based surveillance revealed a decline in influenza virus detection during the regular season compared with previous years. This was observed throughout the implementation of COVID-19 control measures. RSV detection decreased soon after the most stringent COVID-19 control measures commenced; however, an increase in RSV detection was observed after the typical season, following the re-opening of schools and the easing of measures.

Conclusion

COVID-19 non-pharmaceutical interventions led to reduced circulation of influenza and RSV in South Africa. This has limited the country’s ability to provide influenza virus strains for the selection of the annual influenza vaccine. Delayed increases in RSV case numbers may reflect the easing of COVID-19 control measures. An increase in influenza virus detection was not observed, suggesting that the measures may have impacted the two pathogens differently. The impact that lowered and/or delayed influenza and RSV circulation in 2020 will have on the intensity and severity of subsequent annual epidemics is unknown and warrants close monitoring.

Influenza economic burden among potential target risk groups for immunization in South Africa, 2013-2015

BACKGROUND

Data on influenza economic burden in risk groups for severe influenza are important to guide targeted influenza immunization, especially in resource-limited settings. However, this information is limited in low- and middle-income countries.

METHODS

We estimated the cost (from a health system and societal perspective) and years of life lost (YLL) for influenza-associated illness in South Africa during 2013-2015 among (i) children aged 6-59 months, (ii) individuals aged 5-64 years with HIV, pulmonary tuberculosis (PTB) and selected underlying medical conditions (UMC), separately, (iii) pregnant women and (iv) individuals aged ≥65 years, using publicly available data and data collected through laboratory-confirmed influenza surveillance and costing studies. All costs were expressed in 2015 prices using the South Africa all-items Consumer Price Index.

RESULTS

During 2013-2015, the mean annual cost of influenza-associated illness among the selected risk groups accounted for 52.1% ($140.9/$270.5 million) of the total influenza-associated illness cost (for the entire population of South Africa), 45.2% ($52.2/$115.5 million) of non-medically attended illness costs, 43.3% ($46.7/$107.9 million) of medically-attended mild illness costs and 89.3% ($42.0/$47.1 million) of medically-attended severe illness costs. The YLL among the selected risk groups accounted for 86.0% (262,069 /304,867 years) of the total YLL due to influenza-associated death.

CONCLUSION

In South Africa, individuals in risk groups for severe influenza accounted for approximately half of the total influenza-associated illness cost but most of the cost of influenza-associated medically attended severe illness and YLL. This study provides the foundation for future studies on the cost-effectiveness of influenza immunization among risk groups.

The Impact of Human Immunodeficiency Virus Exposure on Respiratory Syncytial Virus-associated Severe Respiratory Illness in South African Infants, 2011-2016

From 2011 through 2016, we conducted surveillance for severe respiratory illness in infants. Human immunodeficiency virus exposure significantly increased the risk of respiratory syncytial virus (RSV)-associated hospitalization in infants aged <5 months. More than 60% of RSV-associated hospitalizations occurred in the first 4 months of life and may be preventable through maternal vaccination or birth-dose monoclonal antibody.

Heterogeneity in influenza seasonality and vaccine effectiveness in Australia, Chile, New Zealand and South Africa: early estimates of the 2019 influenza season

We compared 2019 influenza seasonality and vaccine effectiveness (VE) in four southern hemisphere countries: Australia, Chile, New Zealand and South Africa. Influenza seasons differed in timing, duration, intensity and predominant circulating viruses. VE estimates were also heterogeneous, with all-ages point estimates ranging from 7-70% (I2: 33%) for A(H1N1)pdm09, 4-57% (I2: 49%) for A(H3N2) and 29-66% (I2: 0%) for B. Caution should be applied when attempting to use southern hemisphere data to predict the northern hemisphere influenza season.

Influenza disease burden among potential target risk groups for immunization in South Africa, 2013-2015

BACKGROUND

Data on influenza burden in risk groups for severe influenza are important to guide targeted influenza immunization, especially in resource limited settings. However, this information is limited overall and in particular in low- and middle-income countries. We sought to assess the mean annual national burden of medically and non-medically attended influenza-associated mild, severe-non-fatal and fatal illness among potential target groups for influenza immunization in South Africa during 2013-2015.

METHODS

We used published mean national annual estimates of mild, severe-non-fatal, and fatal influenza-associated illness in South Africa during 2013-2015 and estimated the number of such illnesses occurring among the following risk groups: (i) children aged 6-59 months; (ii) individuals aged 5-64 years with HIV, and/or pulmonary tuberculosis (PTB), and/or selected underlying medical conditions (UMC); (iii) pregnant women; and (iv) individuals aged ≥65 years. We also estimated the number of individuals among the same risk groups in the population.

RESULTS

During 2013-2015, individuals in the selected risk groups accounted for 45.3% (24,569,328/54,086,144) of the population and 43.5% (4,614,763/10,598,138), 86.8% (111,245/128,173) and 94.5% (10,903/11,536) of the mean annual estimated number of influenza-associated mild, severe-non-fatal and fatal illness episodes, respectively. The rates of influenza-associated illness were highest in children aged 6-59 months (23,983 per 100,000 population) for mild illness, in pregnant women (930 per 100,000 population) for severe-non-fatal illness and in individuals aged ≥65 years (138 per 100,000 population) for fatal illness.

CONCLUSION

Influenza immunization of the selected risk groups has the potential to prevent a substantial number of influenza-associated severe illness. Nonetheless, because of the high number of individuals at risk, South Africa, due to financial resources constrains, may need to further prioritize interventions among risk populations. Cost-burden and cost-effectiveness estimates may assist with further prioritization.

The Role of Human Immunodeficiency Virus in Influenza- and Respiratory Syncytial Virus-associated Hospitalizations in South African Children, 2011-2016

BACKGROUND

Data describing influenza- or respiratory syncytial virus (RSV)-associated hospitalized illness in children aged <5 years in Africa are limited.

METHODS

During 2011-2016, we conducted surveillance for severe respiratory illness (SRI) in children aged <5 years in 3 South African hospitals. Nasopharyngeal aspirates were tested for influenza and RSV using real-time reverse transcription polymerase chain reaction. We estimated rates of influenza- and RSV-associated hospitalized SRI by human immunodeficiency virus (HIV) status and compared children who tested positive for influenza vs RSV using multivariable penalized logistic regression.

RESULTS

Among 3650 hospitalized children, 203 (5.6%) tested positive for influenza viruses, 874 (23.9%) for RSV, and 19 (0.5%) for both. The median age of children hospitalized with influenza was 13.9 months vs 4.4 months for RSV (P < .01). Annual influenza-associated hospitalization rates per 100000 were highest among infants aged 6-11 months (545; 95% confidence interval [CI], 409-703), while RSV-associated hospitalization rates were highest in infants aged 0-2 months (6593; 95% CI, 5947-7217). HIV exposure was associated with increased incidence of influenza- and RSV-associated hospitalization in infants aged 0-5 months, with relative risk (RR) 2.2 (95% CI, 1.4-3.4) and 1.4 (95% CI, 1.3-1.6), respectively. HIV infection was associated with increased incidence of influenza- and RSV-associated hospitalization in all age groups; RR 2.7 (95% CI, 2.0-3.5) and 3.8 (95% CI, 3.1-4.8), respectively.

CONCLUSIONS

Influenza- and RSV-associated hospitalizations are common among South African infants. HIV infection and HIV exposure in infants increase risk of influenza- and RSV-associated hospitalization.

Quantifying How Different Clinical Presentations, Levels of Severity, and Healthcare Attendance Shape the Burden of Influenza-associated Illness: A Modeling Study From South Africa

BACKGROUND

Burden estimates of medically and nonmedically attended influenza-associated illness across syndromes and levels of severity are lacking.

METHODS

We estimated the national burden of medically and nonmedically attended influenza-associated illness among individuals with different clinical presentations (all-respiratory, all-circulatory, and nonrespiratory/noncirculatory) and levels of severity (mild, fatal, and severe, nonfatal) using a combination of case-based (from laboratory-confirmed influenza surveillance) and ecological studies, as well as data from healthcare utilization surveys in South Africa during 2013-2015. In addition, we compared estimates of medically attended influenza-associated respiratory illness, obtained from case-based and ecological studies. Rates were reported per 100 000 individuals in the population.

RESULTS

The estimated mean annual number of influenza-associated illness episodes was 10 737 847 (19.8% of 54 096 705 inhabitants). Of these episodes, 10 598 138 (98.7%) were mild, 128 173 (1.2%) were severe, nonfatal, and 11 536 (0.1%) were fatal. There were 2 718 140 (25.6%) mild, 56 226 (43.9%) severe, nonfatal, and 4945 (42.8%) medically attended should be after fatal episodes. Influenza-associated respiratory illness accounted for 99.2% (10 576 146) of any mild, 65.5% (83 941) of any severe, nonfatal, and 33.7% (3893) of any fatal illnesses. Ecological and case-based estimates of medically attended, influenza-associated, respiratory mild (rates: ecological, 1778.8, vs case-based, 1703.3; difference, 4.4%), severe, nonfatal (rates: ecological, 88.6, vs case-based, 75.3; difference, 15.0%), and fatal (rates: ecological, 3.8, vs case-based, 3.5; difference, 8.4%) illnesses were similar.

CONCLUSIONS

There was a substantial burden of influenza-associated symptomatic illness, including severe, nonfatal and fatal illnesses, and a large proportion was nonmedically attended. Estimates, including only influenza-associated respiratory illness, substantially underestimated influenza-associated, severe, nonfatal and fatal illnesses. Ecological and case-based estimates were found to be similar for the compared categories.

Health and economic burden of influenza-associated illness in South Africa, 2013-2015

Background

Economic burden estimates are essential to guide policy‐making for influenza vaccination, especially in resource‐limited settings.

Methods

We estimated the cost, absenteeism, and years of life lost (YLL) of medically and non‐medically attended influenza‐associated mild and severe respiratory, circulatory and non‐respiratory/non‐circulatory illness in South Africa during 2013‐2015 using a modified version of the World Health Organization (WHO) worksheet based tool for estimating the economic burden of seasonal influenza. Additionally, we restricted the analysis to influenza‐associated severe acute respiratory illness (SARI) and influenza‐like illness (ILI; subsets of all‐respiratory illnesses) as suggested in the WHO manual.

Results

The estimated mean annual cost of influenza‐associated illness was $270.5 million, of which $111.3 million (41%) were government‐incurred costs, 40.7 million (15%) were out‐of‐pocket expenses, and $118.4 million (44%) were indirect costs. The cost of influenza‐associated medically attended mild illness ($107.9 million) was 2.3 times higher than that of severe illness ($47.1 million). Influenza‐associated respiratory illness costs ($251.4 million) accounted for 93% of the total cost. Estimated absenteeism and YLL were 13.2 million days and 304 867 years, respectively. Among patients with influenza‐associated WHO‐defined ILI or SARI, the costs ($95.3 million), absenteeism (4.5 million days), and YLL (65 697) were 35%, 34%, and 21% of the total economic and health burden of influenza.

Conclusion

The economic burden of influenza‐associated illness was substantial from both a government and a societal perspective. Models that limit estimates to those obtained from patients with WHO‐defined ILI or SARI substantially underestimated the total economic and health burden of influenza‐associated illness.

The effects of the attributable fraction and the duration of symptoms on burden estimates of influenza-associated respiratory illnesses in a high HIV prevalence setting, South Africa, 2013-2015

BACKGROUND

The attributable fraction of influenza virus detection to illness (INF-AF) and the duration of symptoms as a surveillance inclusion criterion could potentially have substantial effects on influenza disease burden estimates.

METHODS

We estimated rates of influenza-associated influenza-like illness (ILI) and severe acute (SARI-10) or chronic (SCRI-10) respiratory illness (using a symptom duration cutoff of ≤10 days) among HIV-infected and HIV-uninfected patients attending 3 hospitals and 2 affiliated clinics in South Africa during 2013-2015. We calculated the unadjusted and INF-AF-adjusted rates and relative risk (RR) due to HIV infection. Rates were expressed per 100 000 population.

RESULTS

The estimated mean annual unadjusted rates of influenza-associated illness were 1467.7, 50.3, and 27.4 among patients with ILI, SARI-10, and SCRI-10, respectively. After adjusting for the INF-AF, the percent reduction in the estimated rates was 8.9% (rate: 1336.9), 11.0% (rate: 44.8), and 16.3% (rate: 22.9) among patients with ILI, SARI-10, and SCRI-10, respectively. HIV-infected compared to HIV-uninfected individuals experienced a 2.3 (95% CI: 2.2-2.4)-, 9.7 (95% CI: 8.0-11.8)-, and 10.0 (95% CI: 7.9-12.7)-fold increased risk of influenza-associated illness among patients with ILI, SARI-10, and SCRI-10, respectively. Overall 34% of the estimated influenza-associated hospitalizations had symptom duration of >10 days; 8% and 44% among individuals aged <5 and ≥5 years, respectively.

CONCLUSION

The marginal differences between unadjusted and INF-AF-adjusted rates are unlikely to affect policies on prioritization of interventions. HIV-infected individuals experienced an increased risk of influenza-associated illness and may benefit more from annual influenza immunization. The use of a symptom duration cutoff of ≤10 days may underestimate influenza-associated disease burden, especially in older individuals.

Attributable Fraction of Influenza Virus Detection to Mild and Severe Respiratory Illnesses in HIV-Infected and HIV-Uninfected Patients, South Africa, 2012-2016

The attributable fraction (AF) of influenza virus detection to illness has not been described for patients in different age groups or with different HIV infection statuses. We compared the age group–specific prevalence of influenza virus infection among patients with influenza-like illness (ILI) or severe acute or chronic respiratory illness (SARI and SCRI, respectively) with that among controls, stratified by HIV serostatus. The overall AF for influenza virus detection to illness was 92.6% for ILI, 87.4% for SARI, and 86.2% for SCRI. Among HIV-uninfected patients, the AF for all syndromes was highest among persons <1 and >65 years of age and lowest among persons 25–44 years of age; this trend was not observed among HIV-infected patients. Overall, influenza viruses when detected in patients with ILI, SARI, or SCRI are likely attributable to illness. This finding is particularly likely among children and the elderly irrespective of HIV serostatus and among HIV-infected persons irrespective of age.

In- and Out-of-hospital Mortality Associated with Seasonal and Pandemic Influenza and Respiratory Syncytial Virus in South Africa, 2009-2013

Background

Estimates of influenza- and respiratory syncytial virus (RSV)-associated mortality burden are important to guide policy for control. Data are limited on the contribution of out-of-hospital deaths to this mortality.

Methods

We modeled excess mortality attributable to influenza and RSV infection by applying regression models to weekly deaths from national vital statistics from 2009 through 2013, using influenza and RSV laboratory surveillance data as covariates. We fitted separate models for in- and out-of-hospital deaths.

Results

There were 509791 average annual deaths in South Africa, of which 44% (95% confidence interval [CI] 43%-45%) occurred out-of-hospital. Seasonal influenza and RSV all-cause mortality rates were 23.0 (95% CI 11.0-30.6) and 13.2 (95% CI 6.4-33.8) per 100000 population annually (2.3% [95%CI 2.3%-2.4%] and 1.3% [95% CI 1.2%-1.4%] of all deaths respectively). The peak mortality rate was in individuals aged ≥75 years (386.0; 95% CI 176.5-466.3) for influenza and in infants (143.4; 95% CI 0-194.8) for RSV. Overall, 63% (95% CI 62%--65%) of seasonal influenza and 48% (95% CI 47%-49%) of RSV-associated deaths occurred out-of-hospital. Among children aged <5 years, RSV-associated deaths were more likely to occur in-hospital, whereas influenza-associated deaths were more likely to occur out-of-hospital. The mortality rate was 6.7 (95% CI 6.4-33.8) in the first influenza A(H1N1)pdm09 wave in 2009 and 20.9 (95% CI 6.4-33.8) in the second wave in 2011, with 30% (95% CI 29%-32%) of A(H1N1)pdm09-associated deaths in 2009 occurring out-of-hospital.

Discussion

More than 45% of seasonal influenza- and RSV-associated deaths occur out-of-hospital in South Africa. These data suggest that hospital-based studies may substantially underestimate mortality burden.

Epidemiology of influenza B/Yamagata and B/Victoria lineages in South Africa, 2005-2014

Background

Studies describing the epidemiology of influenza B lineages in South Africa are lacking.

Methods

We conducted a prospective study to describe the circulation of influenza B/Victoria and B/Yamagata lineages among patients of all ages enrolled in South Africa through three respiratory illness surveillance systems between 2005 and 2014: (i) the Viral Watch (VW) program enrolled outpatients with influenza-like illness (ILI) from private healthcare facilities during 2005–2014; (ii) the influenza-like illnesses program enrolled outpatients in public healthcare clinics (ILI/PHC) during 2012–2014; and (iii) the severe acute respiratory illnesses (SARI) program enrolled inpatients from public hospitals during 2009–2014. Influenza B viruses were detected by virus isolation during 2005 to 2009 and by real-time reverse transcription polymerase chain reaction from 2009–2014. Clinical and epidemiological characteristics of patients hospitalized with SARI and infected with different influenza B lineages were also compared using unconditional logistic regression.

Results

Influenza viruses were detected in 22% (8,706/39,804) of specimens from patients with ILI or SARI during 2005–2014, of which 24% (2,087) were positive for influenza B. Influenza B viruses predominated in all three surveillance systems in 2010. B/Victoria predominated prior to 2011 (except 2008) whereas B/Yamagata predominated thereafter (except 2012). B lineages co-circulated in all seasons, except in 2013 and 2014 for SARI and ILI/PHC surveillance. Among influenza B-positive SARI cases, the detection of influenza B/Yamagata compared to influenza B/Victoria was significantly higher in individuals aged 45–64 years (adjusted odds ratio [aOR]: 4.2; 95% confidence interval [CI]: 1.1–16.5) and ≥65 years (aOR: 12.2; 95% CI: 2.3–64.4) compared to children aged 0–4 years, but was significantly lower in HIV-infected patients (aOR: 0.4; 95% CI: 0.2–0.9).

Conclusion

B lineages co-circulated in most seasons except in 2013 and 2014. Hospitalized SARI cases display differential susceptibility for the two influenza B lineages, with B/Victoria being more prevalent among children and HIV-infected persons.

Risk Factors for Influenza-Associated Severe Acute Respiratory Illness Hospitalization in South Africa, 2012-2015

Background

Data on risk factors for influenza-associated hospitalizations in low- and middle-income countries are limited.

Methods

We conducted active syndromic surveillance for hospitalized severe acute respiratory illness (SARI) and outpatient influenza-like illness (ILI) in 2 provinces of South Africa during 2012–2015. We compared the characteristics of influenza-positive patients with SARI to those with ILI to identify factors associated with severe disease requiring hospitalization, using unconditional logistic regression.

Results

During the study period, influenza virus was detected in 5.9% (110 of 1861) and 15.8% (577 of 3652) of SARI and ILI cases, respectively. On multivariable analysis factors significantly associated with increased risk of influenza-associated SARI hospitalization were as follows: younger and older age (<6 months [adjusted odds ratio {aOR}, 37.6], 6–11 months [aOR, 31.9], 12–23 months [aOR, 22.1], 24–59 months [aOR, 7.1], and ≥65 years [aOR, 40.7] compared with 5–24 years of age), underlying medical conditions (aOR, 4.5), human immunodeficiency virus infection (aOR, 4.3), and Streptococcus pneumoniae colonization density ≥1000 deoxyribonucleic acid copies/mL (aOR, 4.8). Underlying medical conditions in children aged <5 years included asthma (aOR, 22.7), malnutrition (aOR, 2.4), and prematurity (aOR, 4.8); in persons aged ≥5 years, conditions included asthma (aOR, 3.6), diabetes (aOR, 7.1), chronic lung diseases (aOR, 10.7), chronic heart diseases (aOR, 9.6), and obesity (aOR, 21.3). Mine workers (aOR, 13.8) and pregnant women (aOR, 12.5) were also at increased risk for influenza-associated hospitalization.

Conclusions

The risk groups identified in this study may benefit most from annual influenza immunization, and children <6 months of age may be protected through vaccination of their mothers during pregnancy.

Effectiveness of seasonal influenza vaccination in community-dwelling elderly people: an individual participant data meta-analysis of test-negative design case-control studies

BACKGROUND

Several aggregate data meta-analyses have provided estimates of the effectiveness of influenza vaccination in community-dwelling elderly people. However, these studies ignored the effects of patient-level confounders such as sex, age, and chronic diseases that could bias effectiveness estimates. We aimed to assess the confounder-adjusted effectiveness of influenza vaccines on laboratory-confirmed influenza among elderly people by conducting a global individual participant data meta-analysis.

METHODS

In this individual participant data meta-analysis, we considered studies included in a previously conducted aggregate data meta-analysis that included test-negative design case-control studies published up to July 13, 2014. We contacted all authors of the included studies on Dec 1, 2014, to request individual participant data. Patients were excluded if their unique identifier was missing, their vaccination status was unknown, their outcome status was unknown, or they had had suspected influenza infection more than once in the same influenza season. Cases were patients with influenza-like illness symptoms who tested positive for at least one of A H1N1, A H1N1 pdm09, A H3N2, or B viruses; controls were patients with influenza-like illness symptoms who tested negative for these virus types or subtypes. Influenza vaccine effectiveness against overall and subtype-specific laboratory-confirmed influenza were the primary and secondary outcomes. We used a generalised linear mixed model to calculate adjusted vaccine effectiveness according to vaccine match to the circulating strains of influenza virus and intensity of the virus activity (epidemic or non-epidemic). Vaccine effectiveness was defined as the relative reduction in risk of laboratory-confirmed influenza in vaccinated patients compared with unvaccinated patients. We did subgroup analyses to estimate vaccine effectiveness according to hemisphere, age category, and health status.

FINDINGS

We received 23 of the 53 datasets included in the aggregate data meta-analysis. Furthermore, six additional datasets were provided by data collaborators, which resulted in individual participant data for a total of 5210 participants. A total of 4975 patients had the required data for analysis. Of these, 3146 (63%) were controls and 1829 (37%) were cases. Influenza vaccination was significantly effective during epidemic seasons irrespective of vaccine match status (matched adjusted vaccine effectiveness 44·38%, 95% CI 22·63-60·01; mismatched adjusted vaccine effectiveness 20·00%, 95% CI 3·46-33·68; analyses in the imputed dataset). Seasonal influenza vaccination did not show significant effectiveness during non-epidemic seasons. We found substantial variation in vaccine effectiveness across virus types and subtypes, with the highest estimate for A H1N1 pdm09 (53·19%, 10·25-75·58) and the lowest estimate for B virus types (-1·52%, -39·58 to 26·16). Although we observed no significant differences between subgroups in each category (hemisphere, age, and health status), influenza vaccination showed a protective effect among elderly people with cardiovascular disease, lung disease, or aged 75 years and younger.

INTERPRETATION

Influenza vaccination is moderately effective against laboratory-confirmed influenza in elderly people during epidemic seasons. More research is needed to investigate factors affecting vaccine protection (eg, brand-specific or type-specific vaccine effectiveness and repeated annual vaccination) in elderly people.

FUNDING

University Medical Center Groningen.

Estimating vaccine effectiveness in preventing laboratory-confirmed influenza in outpatient settings in South Africa, 2015

Trivalent seasonal influenza vaccine effectiveness during the 2015 season in South Africa was assessed using a test‐negative case control study design. Influenza A(H1N1)pdm09 was the dominant circulating strain. Overall influenza vaccine coverage was 3.2% (29/899). The vaccine effectiveness estimate, against any influenza virus infection, adjusted for age, underlying conditions and timing within season was 46.2% (95% CI: −23.5 to 76.5), and 53.6% (95% CI: −62.6 to 80.3) against influenza A(H1N1)pdm09.

Effectiveness and knowledge, attitudes and practices of seasonal influenza vaccine in primary healthcare settings in South Africa, 2010-2013

Objectives

Influenza vaccine effectiveness (VE) and coverage data for sub-Saharan Africa are scarce. Using a test-negative case–control design, we estimated influenza VE annually among individuals with influenza-like illness presenting to an outpatient sentinel surveillance programme in South Africa from 2010 to 2013. A knowledge, attitudes and practices (KAP) influenza vaccine survey of programme clinicians was conducted in 2013.

Sample

In total, 9420 patients were enrolled in surveillance of whom 5344 (56.7%) were included in the VE analysis: 2678 (50.1%) were classified as controls (influenza test-negative) and 2666 (49.9%) as cases (influenza test-positive).

Results

Mean annual influenza vaccine coverage among controls was 4.5% for the four years. Annual VE estimates adjusted for age, underlying medical conditions and seasonality for 2010-2013 were 54.2% (95% confidence interval (CI): 2.4–78.6%), 57.1% (95% CI: 15.5–78.2%), 38.4% (95% CI: −71.7–78.1%) and 87.2% (95% CI: 67.2–95.0%), respectively. The KAP survey showed that >90% of clinicians were familiar with the indications for and the benefits of influenza vaccination.

Conclusions

Our study showed that the vaccine was significantly protective in 2010, 2011 and 2013, but not in 2012 when the circulating A(H3N2) strain showed genetic drift. Vaccine coverage was low despite good clinician knowledge of vaccination indications. Further studies are needed to investigate the reason for the low uptake of influenza vaccine.

Deaths associated with respiratory syncytial and influenza viruses among persons ≥5 years of age in HIV-prevalent area, South Africa, 1998-2009(1)

We estimated deaths attributable to influenza and respiratory syncytial virus (RSV) among persons >5 years of age in South Africa during 1998-2009 by applying regression models to monthly deaths and laboratory surveillance data. Rates were expressed per 100,000 person-years. The mean annual number of seasonal influenza-associated deaths was 9,093 (rate 21.6). Persons >65 years of age and HIV-positive persons accounted for 50% (n = 4,552) and 28% (n = 2,564) of overall seasonal influenza-associated deaths, respectively. In 2009, we estimated 4,113 (rate 9.2) influenza A(H1N1)pdm09-associated deaths. The mean of annual RSV-associated deaths during the study period was 511 (rate 1.2); no RSV-associated deaths were estimated in persons >45 years of age. Our findings support the recommendation for influenza vaccination of older persons and HIV-positive persons. Surveillance for RSV should be strengthened to clarify the public health implications and severity of illness associated with RSV infection in South Africa.

Evaluation of influenza vaccine effectiveness and description of circulating strains in outpatient settings in South Africa, 2014

The effectiveness of the trivalent seasonal influenza vaccine during the 2014 season in South Africa was assessed using a test-negative case-control study design including 472 cases and 362 controls. Influenza A(H3N2) was the dominant strain circulating. The overall vaccine effectiveness estimate, adjusted for age and underlying conditions, was 43·1% (95% CI: -26·8-74·5). 2014 H3N2 viruses from South Africa were mainly in sublineage 3C.3 with accumulation of amino acid changes that differentiate them from the vaccine strain in 3C.1.

Mortality Associated With Seasonal and Pandemic Influenza Among Pregnant and Nonpregnant Women of Childbearing Age in a High-HIV-Prevalence Setting-South Africa, 1999-2009

BACKGROUND

Information on the mortality burden associated with seasonal and pandemic influenza virus infection among pregnant women is scarce in most settings, particularly in sub-Saharan Africa where pregnancy and maternal mortality rates as well as human immunodeficiency virus (HIV) prevalence are elevated.

METHODS

We used an ecological study design to estimate the seasonal and A(H1N1)pdm09 influenza-associated mortality among pregnant and nonpregnant women of childbearing age (15-49 years) by HIV serostatus during 1999-2009 in South Africa. Mortality rates were expressed per 100 000 person-years.

RESULTS

During 1999-2009, the estimated mean annual seasonal influenza-associated mortality rates were 12.6 (123 deaths) and 7.3 (914 deaths) among pregnant and nonpregnant women, respectively. Among pregnant women, the estimated mean annual seasonal influenza-associated mortality rates were 74.9 (109 deaths) among HIV-infected and 1.5 (14 deaths) among HIV-uninfected individuals. Among nonpregnant women, the estimated mean annual seasonal influenza-associated mortality rate was 41.2 (824 deaths) among HIV-infected and 0.9 (90 deaths) among HIV-uninfected individuals. Pregnant women experienced an increased risk of seasonal influenza-associated mortality compared with nonpregnant women (relative risk [RR], 2.8; 95% confidence interval [CI], 1.7-3.9). In 2009, the estimated influenza A(H1N1)pdm09-associated mortality rates were 19.3 (181 deaths) and 9.4 (1189 deaths) among pregnant and nonpregnant women, respectively (RR, 3.2; 95% CI, 2.3-4.1).

CONCLUSIONS

Among women of childbearing age, the majority of estimated seasonal influenza-associated deaths occurred in HIV-infected individuals. Pregnant women experienced an increased risk of death associated with seasonal and A(H1N1)pdm09 influenza infection compared with nonpregnant women.

Temporal association in hospitalizations for tuberculosis, invasive pneumococcal disease and influenza virus illness in South African children

Introduction

The seasonal variability in hospitalization for tuberculosis may in part relate to super-imposed bacterial or predisposing respiratory viral infections. We aimed to study the temporal association between hospitalization for culture-confirmed pulmonary tuberculosis (PTB), invasive pneumococcal disease (IPD) and influenza virus epidemics in South African children.

Methods

We undertook a retrospective analysis which examined seasonal trends, from 2005 to 2008, for hospitalization for culture-confirmed PTB and IPD among children in relation to the influenza epidemics in Soweto, South Africa. Original time-series of the influenza virus epidemics and hospitalization rates for PTB and IPD were decomposed into three components: a trend cycle component, a seasonal component and an irregular component using the X-11 seasonal adjustment method. To compare the seasonality amongst the three series, the trend and irregular components were removed and only seasonal components examined.

Results

Across the study period, the influenza virus epidemics peaked during May to July (winter) months, which was closely followed by an increase in the incidence of hospitalization for IPD (August to October) and PTB (August to November).

Discussion

Within- and between-year temporal changes associated with childhood TB hospitalization may in part be driven by factors which influence temporal changes in pneumococcal disease, including potential variability in the severity of influenza virus epidemics in temperate climates. The dynamics of the interplay between the host and these infectious agents appears to be complex and multifactorial.

Mortality associated with seasonal and pandemic influenza and respiratory syncytial virus among children <5 years of age in a high HIV prevalence setting--South Africa, 1998-2009

BACKGROUND

There are few published data describing the mortality burden associated with influenza and respiratory syncytial virus (RSV) infection in children in low- and middle-income countries and particularly from Africa and settings with high prevalence of human immunodeficiency virus (HIV).

METHODS

We modeled the excess mortality attributable to influenza (seasonal and pandemic) and RSV infection by applying Poisson regression models to monthly all-respiratory and pneumonia and influenza deaths, using national influenza and RSV laboratory surveillance data as covariates. In addition, we estimated the seasonal influenza- and RSV-associated deaths among HIV-infected and -uninfected children using Poisson regression models that incorporated HIV prevalence and highly active antiretroviral therapy coverage as covariates.

RESULTS

In children <5 years of age, the mean annual numbers of seasonal influenza- and RSV-associated all-respiratory deaths were 452 (8 per 100 000 person-years [PY]) and 546 (10 per 100 000 PY), respectively. Infants <1 year of age experienced higher mortality rates compared with children 1-4 years of age for both influenza (22 vs 5 per 100 000 PY) and RSV (35 vs 4 per 100 000 PY). HIV-infected compared with HIV-uninfected children <5 years of age were at increased risk of death associated with influenza (age-adjusted relative risk [aRR], 11.5; 95% confidence interval [CI], 9.6-12.6) and RSV (aRR, 8.1; 95% CI, 6.9-9.3) infection. In 2009, we estimated 549 (11 per 100 000 PY) all-respiratory influenza A(H1N1)pdm09-associated deaths among children aged <5 years.

CONCLUSIONS

Our findings support increased research efforts to guide and prioritize interventions such as influenza vaccination and HIV prevention in low- and middle-income countries with high HIV prevalence such as South Africa.

Implications of spatially heterogeneous vaccination coverage for the risk of congenital rubella syndrome in South Africa

Rubella is generally a mild childhood disease, but infection during early pregnancy may cause spontaneous abortion or congenital rubella syndrome (CRS), which may entail a variety of birth defects. Since vaccination at levels short of those necessary to achieve eradication may increase the average age of infection, and thus potentially the CRS burden, introduction of the vaccine has been limited to contexts where coverage is high. Recent work suggests that spatial heterogeneity in coverage should also be a focus of concern. Here, we use a detailed dataset from South Africa to explore the implications of heterogeneous vaccination for the burden of CRS, introducing realistic vaccination scenarios based on reported levels of measles vaccine coverage. Our results highlight the potential impact of country-wide reductions of incidence of rubella on the local CRS burdens in districts with small population sizes. However, simulations indicate that if rubella vaccination is introduced with coverage reflecting current estimates for measles coverage in South Africa, the burden of CRS is likely to be reduced overall over a 30 year time horizon by a factor of 3, despite the fact that this coverage is lower than the traditional 80 per cent rule of thumb for vaccine introduction, probably owing to a combination of relatively low birth and transmission rates. We conclude by discussing the likely impact of private-sector vaccination.

Measles outbreak in South Africa: epidemiology of laboratory-confirmed measles cases and assessment of intervention, 2009-2011

BACKGROUND

Since 1995, measles vaccination at nine and 18 months has been routine in South Africa; however, coverage seldom reached >95%. We describe the epidemiology of laboratory-confirmed measles case-patients and assess the impact of the nationwide mass vaccination campaign during the 2009 to 2011 measles outbreak in South Africa.

METHODS

Serum specimens collected from patients with suspected-measles were tested for measles-specific IgM antibodies using an enzyme-linked immunosorbent assay and genotypes of a subset were determined. To estimate the impact of the nationwide mass vaccination campaign, we compared incidence in the seven months pre- (1 September 2009-11 April 2010) and seven months post-vaccination campaign (24 May 2010-31 December 2010) periods in seven provinces of South Africa.

RESULTS

A total of 18,431 laboratory-confirmed measles case-patients were reported from all nine provinces of South Africa (cumulative incidence 37 per 100,000 population). The highest cumulative incidence per 100,000 population was in children aged <1 year (603), distributed as follows: <6 months (302/100,000), 6 to 8 months (1083/100,000) and 9 to 11 months (724/100,000). Forty eight percent of case-patients were ≥ 5 years (cumulative incidence 54/100,000). Cumulative incidence decreased with increasing age to 2/100,000 in persons ≥ 40 years. A single strain of measles virus (genotype B3) circulated throughout the outbreak. Prior to the vaccination campaign, cumulative incidence in the targeted vs. non-targeted age group was 5.9-fold higher, decreasing to 1.7 fold following the campaign (P<0.001) and an estimated 1,380 laboratory-confirmed measles case-patients were prevented.

CONCLUSION

We observed a reduction in measles incidence following the nationwide mass vaccination campaign even though it was conducted approximately one year after the outbreak started. A booster dose at school entry may be of value given the high incidence in persons >5 years.

Regional perspectives on influenza surveillance in Africa

Africa possesses little capacity for influenza surveillance-Senegal and South Africa being the only countries in the WHO African region who regularly pursue active surveillance and characterize influenza isolates. South Africa has three sites-in Cape Town, Durban and the largest in Johannesburg at the National Institute for Virology (NIV). The NIV antigenically and molecularly characterizes influenza viruses isolated from specimens provided by a sentinel network of approximately 50 clinical sites. This information, together with the isolates themselves are supplied to WHO International Influenza Centres in London and Melbourne. In addition, proxy markers of influenza severity such as school absenteeism and doctor/clinic visits are monitored to assess the severity of epidemics. Although, influenza exacts a heavier toll of the illness burden in developing countries already beset with underlying chronic medical conditions and also has a more severe impact on economies largely dependent on single income earners and subsistence farmers, influenza surveillance and vaccination awareness is woefully lacking on the African continent, and this urgently needs to be remedied.

Seroprevalence to polio in personnel at a virology institute

OBJECTIVES

To determine the level of immunity to polio in adult personnel at the National Institute for Virology (NIV), South Africa.

METHODS

Polio neutralizing antibodies results on 776 NIV staff members tested between 1979 and 1999 and seroresponses in seronegative personnel given a booster vaccination were analysed.

RESULTS

613 of the 776 (79%) personnel had neutralizing polio antibodies to all three types, independent of age, gender, race or job category. Types 1 and 2 antibodies were found in 92% and 94%, respectively, but type 3 was less prevalent at 87%. Of the 93 persons seronegative to one or more types, 13 failed to respond to the first booster vaccination and 8 remained as non-responders after two booster vaccinations. Of the 19 personnel who were bled four days after booster vaccination, 16 (84%) had already developed an antibody response.

CONCLUSIONS

Most (79%) adult laboratory personnel retained detectable levels of neutralizing antibodies to polio, independent of age, gender, race or job category, and even in those persons lacking detectable antibodies, most (84%) responded with a secondary immune response. Nevertheless the immunity gap, particularly to type 3, mandates routine screening of personnel potentially exposed to wild-type polio virus and a booster vaccination for seronegatives.

A population-based seroprevalence study in South Africa as a tool in the polio eradication initiative

A seroprevalence study for poliomyelitis was carried out on a sample of sera from a serum bank used for a vitamin A study. Vaccination coverage was satisfactory (80% or more) in five of nine provinces, although a prevalence of antibody to polio of 80% or more was found in all provinces. Serologic immunity (i.e., the prevalence of neutralizing antibodies) exceeded vaccination coverage, suggesting secondary spread of vaccine virus. However, whether or not water was supplied through a piped system was not associated with secondary spread of vaccine virus to nonvaccinated children. Seroprevalence studies are a valuable adjunct to acute flaccid paralysis surveillance, which is the standard surveillance instrument for the poliomyelitis eradication initiative. The use of available and suitable serum banks for seroprevalence investigations is a relatively cheap monitoring option that can yield very valuable information for the eradication initiative.

Surveillance of respiratory viruses. A 10-year laboratory-based study

Respiratory virus isolates made at the National Institute for Virology from 1982 to 1991 were studied. An active virus surveillance programme, 'viral watch', which recruits throat swab specimens from a network of monitoring centres--mainly in the Witwatersrand and Vereeniging area with one centre in Middelburg--that represent a cross-section of the population, provided 68% of the specimens and 74% of the isolates, with an isolation rate of 25.5%. This was significantly higher than that of routine specimens (17.7%). Of the 966 isolates, influenza viruses accounted for 527 (54.7%), para-influenza for 122 (12.6%), respiratory syncytial virus for 34 (3.4%) and adenovirus for 106 (11.0%). Influenza viruses showed a definite seasonal peak between June and August whereas the other viruses, although they showed a winter predominance, were isolated throughout the year. An active virus surveillance programme is particularly valuable in monitoring respiratory virus epidemiology in the population.

The current epidemiology of hepatitis A infection in South Africa: implications for vaccination

Testing stored sera from various categories of individuals has shown that among the Black population hepatitis A virus (HAV) infection is universal and most adult Black subjects are immune. Infection probably occurs early in life, consistent with the epidemiological pattern seen in the developing world. By contrast, seroprevalence of HAV infection in adult White subjects increases with age, reflecting an epidemiological pattern seen in the developed world. White subjects working in a virological laboratory and White medical students had comparatively low seroprevalences of HAV infection and could therefore represent groups at risk. Hepatitis A vaccine is likely to be available in South Africa in the near future and could be offered to these groups. Pre-vaccination immunity screening would be a cost-effective strategy.

Hepatitis B virus prevalence in two institutions for the mentally handicapped

A comparative study of the prevalence of hepatitis B virus infection in two institutions for the mentally handicapped was carried out between April and November 1989 and April and August 1991. The institutions were situated within 10 km of each other in north-eastern Johannesburg. One institution had a significantly higher prevalence of virus markers, 68% (139 of 203) compared with 23% (40 of 176), was in poorer condition and had more severely handicapped residents with more aggressive behaviour. However, the most important difference between the two institutions was that residents at the higher-prevalence institution were admitted at a considerably younger age. Younger individuals appear to be more susceptible to infection and are more likely to develop persistent infection, thus contributing to a greater pool of infection in the institution.

Primary and secondary infection with human parvovirus B19 in pregnant women in South Africa

A study of human parvovirus B19 infection in 1,967 pregnant women of all races in Johannesburg revealed an overall prevalence of 24.9% for IgG antibodies and 3.3% for IgM antibodies. Of the 64 IgM-positive sera indicating active infection, 62 were resistant to urea denaturation. No differences in the prevalence of IgG antibodies between population groups were observed, but active infections, as demonstrated by IgM antibodies, were significantly more prevalent in black than in white, coloured or Asian mothers.

Is antenatal screening for rubella and cytomegalovirus justified?

Altogether 2,250 asymptomatic pregnant women attending an antenatal clinic were investigated for serological evidence of past exposure to rubella and cytomegalovirus (CMV) as well as for active primary infection or reinfection/reactivation. Only 7 (0.3%) active rubella infections were diagnosed, none of them primary. Similarly, out of 132 patients with active CMV, only 5 primary infections (3.8%) were diagnosed; the vast majority--127 (96%)--had reactivation infections. No congenital rubella infections were detected, while the transplacental transmission rate for CMV was 6.4%. None of the infants followed up was clinically affected at birth or at 6 months. No racial differences in seroprevalences for CMV or rubella immunoglobulin were observed, but immunoglobulin antibody prevalence to CMV was significantly lower in the white group. From this study there appeared to be no indication for routine antenatal screening for CMV in asymptomatic mothers.

Observations of subacute sclerosing panencephalitis in South Africa

Analysis of 75 cases of subacute sclerosing panencephalitis (SSPE) reported to the National Institute for Virology, South Africa, in 1984-1990 does not support the role of intensive exposure to measles virus in the pathogenesis of SSPE. The incidence of SSPE per million population was similar in Blacks and Whites, although that of reported measles is up to 10 times greater in Blacks. The age of SSPE follows the distribution of measles cases; thus, significantly more younger SSPE cases were found in Blacks than in Whites. The distribution between males and females was approximately equal. These data suggest SSPE to be a fortuitous complication of measles infection associated with as yet unidentified risk factors rather than a consequence of an excessive dose of infecting virus or immunological immaturity.

The role of sexual transmission in the epidemiology of hepatitis C virus in black South Africans

The role of sexual transmission of hepatitis C virus in Black South Africans was evaluated by a seroprevalence study of sentinel populations at varying risk for sexually transmitted diseases (STD). Prevalence of anti-hepatitis C virus antibodies was found to be 1.8% in an STD clinic sample of 272, 0.7% in a family planning sample of 148, 3.3% in a sample of 246 'blue collar' workers (81% of rural origin), and 0.9 in a sample of 117 new blood donors. All samples were from Black adults. The differences between them were not significant (P = 0.2348). In contrast, the prevalence of anti-human immunodeficiency virus antibodies in the STD sample (5.5%) was statistically significantly different (P = 0.00095) from the family planning clinic sample (1.4%) and the blue collar sample (0.8%) as well as from the reported prevalence for black blood donors in the Johannesburg area (0.7%). No evidence supporting a role for sexual transmission of hepatitis C virus was found, while the prevalence of infection appeared to be higher in rural populations and in males. These features are similar to hepatitis B in this population.

Low antibody avidity in elderly chickenpox patients

A small outbreak of chickenpox confirmed serologically in 3 elderly patients from a geriatric home is described. Disease was probably due to exogenous reinfection, yet nevertheless the avidity of specific antibodies measured by the urea denaturation test was even lower than in primary chickenpox controls, which themselves were, as expected, significantly lower than zoster controls. In elderly individuals susceptibility to reinfection with varicella-zoster virus (VZV) with clinical manifestation such as chickenpox may well be associated with the decay of specific humoral immunity detectable by antibodies of particularly low avidity, in contrast to reactivation of latent VZV presenting clinically as zoster, which is related to deficiencies in specific cellular immunity.

Poliomyelitis outbreak in Natal/KwaZulu, South Africa, 1987-1988. 2. Immunity aspects

An extensive poliomyelitis outbreak due to type 1 poliovirus took place in Natal/KwaZulu, South Africa, in 1987-1988, causing 412 paralytic cases. This epidemic differed from a previously described outbreak in Gazankulu, South Africa, in 1982 in that it occurred against a background of relatively good immunity. Thus, only 12% of patients lacked antibodies to types 2 and 3, indicating lack of previous immunization, and 76% of healthy children sampled in the epidemic area had serological immunity to all 3 types of poliovirus. The occurrence of extensive outbreaks in relatively well-immunized communities emphasizes the need to maximize herd immunity and reduce reservoirs of infection in the gut and in the environment, which can be achieved only with oral polio vaccine.

Poliomyelitis outbreak in Natal/KwaZulu, South Africa, 1987-1988. 1. Epidemiology

An epidemic of type 1 poliomyelitis occurred in Natal/KwaZulu in the eastern part of South Africa between December 1987 and November 1988. 412 poliomyelitis cases were reported, of whom 74% were younger than 5 years. The case-fatality rate was 8%. It is suggested that massive floods, experienced in the area 2 months earlier, triggered the outbreak.

Integration of hepatitis B vaccination into rural African primary health care programmes

OBJECTIVE

To determine the efficacy of hepatitis B vaccine when added to the routine expanded programme on immunisation under field conditions in rural Africa.

DESIGN

Infants were immunised according to two schedules--an early schedule at birth, 3 months, and 6 months and a later schedule to correspond with routine vaccination in the expanded programme on immunisation at 3 months, 4 1/2 months, and 6 months.

SETTING

Venda, northern Transvaal, South Africa, a self governing region of 7460 square kilometers varying from rural villages to small towns.

SUBJECTS

The 1989 birth cohort of Venda.

MAIN OUTCOME MEASURES

Coverage for hepatitis B vaccine at first, second, and third doses; serological assessment of vaccine efficacy by prevalence of antibodies to hepatitis B surface antigen in infants who had completed the three dose course of immunisation; antibodies to hepatitis B core antigen to determine if natural infection occurred.

RESULTS

Vaccine coverage for hepatitis B dropped sharply from 99% to 53% to 39% for the first, second, and third dose respectively. In contrast, vaccine coverage was maintained at 97-99% for the three doses of poliomyelitis vaccine. Serological evaluation of vaccine efficacy showed that only 3.5% of recipients of all three doses failed to develop antibodies to hepatitis B surface antigen. Only 6.6% of vaccine recipients were vaccinated according to either the early or later schedules whereas 93.4% received their doses of vaccine at intervals beyond the limits of either of the planned schedules. There was, however, no significant difference in seroconversion to the surface antigen between the "unscheduled" or scheduled groups of those who were vaccinated according to the early or late schedules. The pattern of prevalence of antibodies to hepatitis B core antigen, which showed a sharp fall in children aged over 7 months, suggested that the antibodies were acquired passively rather than by active infection.

CONCLUSIONS

Supplementation of the present expanded programme on immunisation with hepatitis B vaccine in rural Africa is fraught with difficulties. However, the vaccine was effective within a fairly wide spacing of dosage. Adding hepatitis B vaccine to diphtheria, tetanus, and pertussis as a tetravalent vaccine is proposed as a means of effectively integrating it into the expanded programme on immunisation in Third World settings.

Measles, mumps and rubella immunization at nine months in a developing country

The antibody responses and reactogenicity of a measles, mumps and rubella vaccine in 9-month-old and 15-month-old black children in South Africa were compared. The antibody response to the measles component was marginally better in the older group, but no differences were observed in the response to the mumps and rubella components. Reactogenicity was similar in the two age groups. Therefore it is possible that a trivalent measles, mumps and rubella vaccine can safely and effectively replace routine measles immunization at 9 months of age in this population. Whether routine immunization policy should incorporate such a vaccine depends on the extent of acceptance of measles vaccination. In urban populations of developing countries with high rates of measles immunization, routine vaccination at 9 months might interrupt circulating wild type rubella and provide sufficient herd immunity to protect susceptible women of childbearing age. It also should decrease significantly the complications associated with wild type mumps infection. The replacement of measles vaccine by a trivalent vaccine may be very cost-effective.

Susceptibility to poliomyelitis, measles, mumps and rubella in university students

A serological study of 433 university students in various health care professions revealed levels of susceptibility of 2-7% for measles, 0-4% for mumps, 6-17% for poliomyelitis and a particularly disquieting 13-23% for rubella. Representing a developed population with a supposedly high level of immunisation cover these levels of susceptibility indicate students' vulnerability to outbreaks caused by viruses coming from reservoirs in under-immunised developing populations in the country. Nevertheless, no evidence of occupational exposure between the first- and final-year students was revealed. Immunisation efforts thus need to be urgently targeted not only to developing but also to developed populations in South Africa.

Laboratory studies of the 1984 influenza epidemic on the Witwatersrand

A particularly severe outbreak of influenza occurred on the Witwatersrand from May to August 1984, caused sequentially by influenza A (H3N2), B/influenza and influenza A (H1N1) viruses. Although the precise extent of the infection was impossible to determine, valuable anecdotal information was provided by a network of sentinel sampling stations in private practices, clinics and hospitals, representing a cross-section of population groups on the Witwatersrand. This active surveillance programme was invaluable in providing some 85% of all the specimens, the remainder being routine clinical specimens; in addition, isolation was approximately twice as efficient for the actively acquired specimens than for the routine ones. The epidemic affected all individuals approximately equally, regardless of age, race or socio-economic status. Infection with H1N1 virus tended to predominate in the younger age group, 78% of isolates being from subjects under 30 years of age, whereas 71% of H3N2 isolates came from subjects over 30 years of age. The B/influenza isolates tended to be more evenly dispersed. Novel strains of B/influenza and H1N1 viruses were introduced into the country and possibly contributed to the greater than usual severity of the epidemic. An active surveillance programme is essential to monitor the extent of influenza virus activity and to alert virologists to the introduction of new strains, although at present forecasting of future influenza epidemics is not possible with any significant degree of reliability.

Tetanus antibodies as a marker of potential efficacy of killed polio immunization

The use of antibodies to tetanus toxin as a marker of efficacy of parenteral immunization was examined in a randomized sample of 1212 sera representative of the total black infant population of the RSA between 24 and 35 months. All but one of these sera had protective levels of antibodies measured by enzyme-linked immunosorbent assay. In contrast, in a previous study only 59-80% had tritypic immunity to polio and 70-84% mono- or bitypic immunity. Thus, this serological marker was found to be unreliable and some possibilities for this remarkably high level of antitetanus antibodies are considered.

A comprehensive investigation of immunity to poliomyelitis in a developing country

A comprehensive nationwide surveillance program of serologic immunity of two-year-old black children, combined with evaluation of vaccine quality and distribution, was carried out in South Africa during 1983-1984. Sera were randomly collected from urban and rural groups and cluster samples collected from the semi-urban group. The sample represented 0.23% of the total target population. Satisfactory levels of immunity were found in the urban (80%) and semi-urban (71%) groups but a disquietingly low level was found for the rural group (59%). Individual districts in the rural group could be singled out for directed cluster sampling at a later stage. History and documentation of immunization corresponded well to serologic findings and revealed also a fairly substantial level of natural immunization among individuals who, on history, had received no vaccine. Some 95% of random samples of vaccine recalled from the field showed satisfactory levels of potency. An immunity surveillance program such as this is ideally suited and highly cost-effective for developing countries with incomplete immunization to prevent large-scale buildup of immunity deficit. The technique, however, is too insensitive to detect localized community immunity defects.

Epidemic Coxsackie B virus infection in Johannesburg, South Africa

A particularly extensive epidemic of Coxsackie B3 virus infection occurred in Johannesburg in the spring and summer of 1984. A total of 142 positive cases were diagnosed by isolation of the virus from stools and other specimens (60) or by serology (82). Coxsackie B3 accounted for 87% of the isolations and was also the dominant serotype on serology. The outbreak involved predominantly children and young adults, with no apparent sex differences being noted. The majority of specimens came from the white population and no significant difference in age or sex distribution could be observed between the two race groups. The major clinical presentation in the white group was Bornholm disease followed by cardiac involvement and then meningoencephalitis. In the black group, however, myocarditis was the major clinical presentation, which is of particular interest taking into account the extremely high incidence of acute rheumatic carditis in this population and the prevalence of chronic cardiomyopathy.

Laboratory monitoring of rubella

A study was undertaken to determine the level of immunity to rubella in the population on the basis of findings in serum specimens sent to the laboratory of the National Institute for Virology. A total of 4791 sera taken between August 1982 and October 1983 were examined for rubella-specific IgG antibodies by enzyme-linked immunosorbent assay (ELISA). A disquietingly high proportion (18,4%) of women of child-bearing age were not immune; 59 cases of primary infection occurred in pregnant women, as documented by the presence of rubella-specific IgM antibodies on ELISA. The need to ensure the protection of susceptible women of child-bearing age by prepubertal immunization and screening for immunity is emphasized.