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Journal ArticleDOI

Influenza seasonality and vaccination timing in tropical and subtropical areas of southern and south-eastern Asia

TL;DR: Most southern and south-eastern Asian countries lying north of the equator should consider vaccinating against influenza from April to June; countries near the equators without a distinct peak in influenza activity can base vaccination timing on local factors.
Abstract: Objective To characterize influenza seasonality and identify the best time of the year for vaccination against influenza in tropical and subtropical countries of southern and south-eastern Asia that lie north of the equator. Methods Weekly influenza surveillance data for 2006 to 2011 were obtained from Bangladesh, Cambodia, India, Indonesia, the Lao People's Democratic Republic, Malaysia, the Philippines, Singapore, Thailand and Viet Nam. Weekly rates of influenza activity were based on the percentage of all nasopharyngeal samples collected during the year that tested positive for influenza virus or viral nucleic acid on any given week. Monthly positivity rates were then calculated to define annual peaks of influenza activity in each country and across countries. Findings Influenza activity peaked between June/July and October in seven countries, three of which showed a second peak in December to February. Countries closer to the equator had year-round circulation without discrete peaks. Viral types and subtypes varied from year to year but not across countries in a given year. The cumulative proportion of specimens that tested positive from June to November was > 60% in Bangladesh, Cambodia, India, the Lao People's Democratic Republic, the Philippines, Thailand and Viet Nam. Thus, these tropical and subtropical countries exhibited earlier influenza activity peaks than temperate climate countries north of the equator. Conclusion Most southern and south-eastern Asian countries lying north of the equator should consider vaccinating against influenza from April to June; countries near the equator without a distinct peak in influenza activity can base vaccination timing on local factors.

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Journal ArticleDOI
TL;DR: Year-round maternal influenza immunisation significantly reduced maternal influenza-like illness, influenza in infants, and low birthweight over the entire course of the study, indicating the strategy could be useful in subtropical regions.
Abstract: Summary Background Influenza immunisation during pregnancy is recommended but not widely implemented in some low-income regions We assessed the safety and efficacy in mothers and infants of year-round maternal influenza immunisation in Nepal, where influenza viruses circulate throughout the year Methods In this phase 4, randomised, placebo-controlled trial, we enrolled two consecutive sequential annual cohorts of pregnant women from the Sarlahi district in southern Nepal We randomised mothers 1:1 to receive seasonally recommended trivalent inactivated influenza vaccine or saline placebo in blocks of eight, stratified by gestational age at enrolment (17–25 weeks vs 26–34 weeks) Women were eligible if they were married, 15–40 years of age, 17–34 weeks' gestation at enrolment, and had not previously received any influenza vaccine that season We collected serum samples before and after immunisation, and cord blood from a subset of women and infants Staff masked to allocation made home visits every week from enrolment to 6 months after delivery Midnasal swabs for respiratory virus PCR testing were collected during maternal acute febrile respiratory infections, and from infants with any respiratory symptom We assessed vaccine immunogenicity, safety, and three primary outcomes: the incidence of maternal influenza-like illness in pregnancy and 0–180 days postpartum, the incidence of low birthweight ( Findings From April 25, 2011, to Sept 9, 2013, we enrolled 3693 women in two cohorts of 2090 (1041 assigned to placebo and 1049 to vaccine) and 1603 (805 assigned to placebo and 798 to vaccine), with 3646 liveborn infants (cohort 1, 999 in placebo group and 1010 in vaccine group; cohort 2, 805 in placebo group and 798 in vaccine group) Immunisation reduced maternal febrile influenza-like illness with an overall efficacy of 19% (95% CI 1 to 34) in the combined cohorts; 9% efficacy (−16 to 29) in the first cohort, and 36% efficacy (9 to 55) in the second cohort For laboratory-confirmed influenza infections in infants aged 0–6 months, immunisation had an overall efficacy for the combined cohorts of 30% (95% CI 5 to 48); in the first cohort, the efficacy was 16% (−19 to 41), and in the second cohort it was 60% (26 to 88) Maternal immunisation reduced the rates of low birthweight by 15% (95% CI 3–25) in both cohorts combined The rate of small for gestational age infants was not modified by immunisation The number of adverse events was similar regardless of immunisation status Miscarriage occurred in three (0·2%) participants in the placebo group versus five (0·3%) in the vaccine group, stillbirth occurred in 31 (1·7%) versus 33 (1·8%), and congenital defects occurred in 18 (1·0%) versus 20 (1·1%) Five women died in the placebo group and three died in the vaccine group The number of infant deaths at age 0–6 months was similar in each group (50 in the placebo group and 61 in the vaccine group) No serious adverse events were associated with receipt of immunisation Interpretation Year-round maternal influenza immunisation significantly reduced maternal influenza-like illness, influenza in infants, and low birthweight over the entire course of the study, indicating the strategy could be useful in subtropical regions Funding Bill & Melinda Gates Foundation

166 citations

Journal ArticleDOI
TL;DR: The Global Influenza B Study aims to collect information on global epidemiology and burden of disease of influenza B since 2000.
Abstract: The Global Influenza B Study includes the following members: Juan Manuel Rudi, Instituto Nacional de Enfermedades Respiratorias ‘Dr. Emilio Coni’, Santa Fe, Argentina; Rhonda Owen, Influenza Surveillance Section, Surveillance Branch, Office of Health Protection, Department of Health and Ageing, Woden, Australia; Kunzang Dorji, Public Health Laboratory, Department of Public Health, Ministry of Health, Thimphu, Bhutan; Jose Ricardo Pio Marins and Walquiria Aparecida Ferreira de Almeida, Ministry of Health, Brasilia, DF, Brazil; Marie-Astrid Vernet and Guy Vernet, Service de Virologie, Centre Pasteur du Cameroun, Yaounde, Cameroon; Winston Andrade, Seccion de Virus Respiratorios y Exantematicos, Instituto de Salud Publica de Chile, Santiago de Chile, Chile; Juan Yang and Ming Li, Division of Infectious Disease, Key Laboratory of Surveillance and Early-warning on Infectious Disease, Chinese Center for Disease Control and Prevention, Beijing, China; Jenny Lara, National Influenza Center, Ministry of Health, San Jose, Costa Rica; Celina de Lozano, National Influenza Center, Ministry of Health, San Salvador, El Salvador; Richard Pebody, Joanna Ellis and Helen Green, Respiratory Diseases Department, Public Health England, Colindale, UK; Leticia Castillo, National Influenza Center, Ministry of Health, Guatemala City, Guatemala; Maria Luisa Matute, National Influenza Center, Ministry of Health, Tegucigalpa, Honduras; Nurhayati, Ministry of Health, Republic of Indonesia, and US Naval Medical Research Unit No. 2, Jakarta Indonesia; Isabella Donatelli, National Influenza Center, Istituto Superiore Sanita, Rome, Italy; Coulibaly Daouda, National Institute of Public Hygiene, Abidjan, Cote d’Ivoire; Joshua A. Mott, US Centers for Disease Control and Prevention, Nairobi, Kenya; Norosoa Harline Razanajatovo, National Influenza Center, Virology Unit, Institut Pasteur of Madagascar, Antananarivo, Madagascar; Laurence Randrianasolo, Epidemiology Unit, Institut Pasteur of Madagascar, Antananarivo, Madagascar; Liza Lopez, Institute of Environmental Science and Research, Wellington, New Zealand; Angel Balmaseda, National Influenza Center, Ministry of Health, Managua, Nicaragua; Brechla Moreno, National Influenza Center, IC Gorgas, Panama City, Panama; Jeffrey Cutter, Communicable Diseases Division, Ministry of Health, Singapore, Singapore; Vernon J. Lee, Communicable Diseases Division, Ministry of Health, Singapore, and Saw Swee Hock School of Public Health, National University of Singapore, Singapore; Cheryl Cohen, Centre for Respiratory Diseases and Meningitis (CRDM), National Institute for Communicable Diseases, Johannesburg, South Africa, and School of Public Health, Faculty of Health Science, University of the Witwatersrand, Johannesburg, South Africa; Selim Badur, Istanbul University, Istanbul, Turkey; Larysa Radchenko, L.V. Gromashevsky Institute of Epidemiology and Infectious Diseases National Academy of Medical Science of Ukraine, Kiev, Ukraine; Joseph Bresee, Epidemiology and Prevention Branch, Influenza Division, Centers for Disease Control and Prevention, Atlanta, GA, USA.

145 citations

Journal ArticleDOI
27 Apr 2016-PLOS ONE
TL;DR: Distinct influenza seasonality patterns, though complex, could be ascertained for most countries in the tropics and subtropics using national surveillance data and it may be possible to group countries into zones based on similar recommendations for vaccine timing and formulation.
Abstract: Background The timing of the biannual WHO influenza vaccine composition selection and production cycle has been historically directed to the influenza seasonality patterns in the temperate regions of the northern and southern hemispheres. Influenza activity, however, is poorly understood in the tropics with multiple peaks and identifiable year-round activity. The evidence-base needed to take informed decisions on vaccination timing and vaccine formulation is often lacking for the tropics and subtropics. This paper aims to assess influenza seasonality in the tropics and subtropics. It explores geographical grouping of countries into vaccination zones based on optimal timing of influenza vaccination. Methods Influenza seasonality was assessed by different analytic approaches (weekly proportion of positive cases, time series analysis, etc.) using FluNet and national surveillance data. In case of discordance in the seasonality assessment, consensus was built through discussions with in-country experts. Countries with similar onset periods of their primary influenza season were grouped into geographical zones. Results The number and period of peak activity was ascertained for 70 of the 138 countries in the tropics and subtropics. Thirty-seven countries had one and seventeen countries had two distinct peaks. Countries near the equator had secondary peaks or even identifiable year-round activity. The main influenza season in most of South America and Asia started between April and June. The start of the main season varied widely in Africa (October and December in northern Africa, April and June in Southern Africa and a mixed pattern in tropical Africa). Eight “influenza vaccination zones” (two each in America and Asia, and four in Africa and Middle East) were defined with recommendations for vaccination timing and vaccine formulation. The main limitation of our study is that FluNet and national surveillance data may lack the granularity to detect sub-national variability in seasonality patterns. Conclusion Distinct influenza seasonality patterns, though complex, could be ascertained for most countries in the tropics and subtropics using national surveillance data. It may be possible to group countries into zones based on similar recommendations for vaccine timing and formulation.

140 citations


Cites background or result from "Influenza seasonality and vaccinati..."

  • ...In the context where a country with no data adjoined neighbours that belonged to different zones, the country was grouped with the neighbour that shared the same latitude [12,17,18]....

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  • ...As seen in other studies, countries situated near to the equator were likely to have multiple peaks with or without identifiable year-round activity [18]....

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Journal ArticleDOI
TL;DR: The effects of daily local meteorological data from Edinburgh, Scotland on the seasonal variations in viral transmission was examined and the relationship between meteorological factors and viral seasonality was investigated.
Abstract: Numerous viruses can cause upper respiratory tract infections. They often precede serious lower respiratory tract infections. Each virus has a seasonal pattern, with peaks in activity in different seasons. We examined the effects of daily local meteorological data (temperature, relative humidity, “humidity-range” and dew point) from Edinburgh, Scotland on the seasonal variations in viral transmission. We identified the seasonality of rhinovirus, adenovirus, influenza A and B viruses, human parainfluenza viruses 1–3 (HPIV), respiratory syncytial virus (RSV) and human metapneumovirus (HMPV) from the 52060 respiratory samples tested between 2009 and 2015 and then confirmed the same by a generalised linear model. We also investigated the relationship between meteorological factors and viral seasonality. Non-enveloped viruses were present throughout the year. Following logistic regression adenovirus, influenza viruses A, B, RSV and HMPV preferred low temperatures; RSV and influenza A virus preferred a narrow “humidity-range” and HPIV type 3 preferred the season with lower humidity. A change (i.e. increase or decrease) in specific meteorological factors is associated with an increase in activity of specific viruses at certain times of the year.

123 citations


Cites background from "Influenza seasonality and vaccinati..."

  • ...IAV is known to occur throughout the year in South East Asian countries closer to the equator (warm, humid environment) 38 ....

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References
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Journal ArticleDOI
TL;DR: Influenza vaccines can provide moderate protection against virologically confirmed influenza, but such protection is greatly reduced or absent in some seasons.
Abstract: Summary Background No published meta-analyses have assessed efficacy and effectiveness of licensed influenza vaccines in the USA with sensitive and highly specific diagnostic tests to confirm influenza. Methods We searched Medline for randomised controlled trials assessing a relative reduction in influenza risk of all circulating influenza viruses during individual seasons after vaccination (efficacy) and observational studies meeting inclusion criteria (effectiveness). Eligible articles were published between Jan 1, 1967, and Feb 15, 2011, and used RT-PCR or culture for confirmation of influenza. We excluded some studies on the basis of study design and vaccine characteristics. We estimated random-effects pooled efficacy for trivalent inactivated vaccine (TIV) and live attenuated influenza vaccine (LAIV) when data were available for statistical analysis (eg, at least three studies that assessed comparable age groups). Findings We screened 5707 articles and identified 31 eligible studies (17 randomised controlled trials and 14 observational studies). Efficacy of TIV was shown in eight (67%) of the 12 seasons analysed in ten randomised controlled trials (pooled efficacy 59% [95% CI 51–67] in adults aged 18–65 years). No such trials met inclusion criteria for children aged 2–17 years or adults aged 65 years or older. Efficacy of LAIV was shown in nine (75%) of the 12 seasons analysed in ten randomised controlled trials (pooled efficacy 83% [69–91]) in children aged 6 months to 7 years. No such trials met inclusion criteria for children aged 8–17 years. Vaccine effectiveness was variable for seasonal influenza: six (35%) of 17 analyses in nine studies showed significant protection against medically attended influenza in the outpatient or inpatient setting. Median monovalent pandemic H1N1 vaccine effectiveness in five observational studies was 69% (range 60–93). Interpretation Influenza vaccines can provide moderate protection against virologically confirmed influenza, but such protection is greatly reduced or absent in some seasons. Evidence for protection in adults aged 65 years or older is lacking. LAIVs consistently show highest efficacy in young children (aged 6 months to 7 years). New vaccines with improved clinical efficacy and effectiveness are needed to further reduce influenza-related morbidity and mortality. Funding Alfred P Sloan Foundation.

1,579 citations

Journal ArticleDOI
TL;DR: Differences in AH provide a single, coherent, more physically sound explanation for the observed variability of IVS, IVT and influenza seasonality in temperate regions and can be further tested through future, additional laboratory, epidemiological and modeling studies.
Abstract: Influenza A incidence peaks during winter in temperate regions. The basis for this pronounced seasonality is not understood, nor is it well documented how influenza A transmission principally occurs. Previous studies indicate that relative humidity (RH) affects both influenza virus transmission (IVT) and influenza virus survival (IVS). Here, we reanalyze these data to explore the effects of absolute humidity on IVT and IVS. We find that absolute humidity (AH) constrains both transmission efficiency and IVS much more significantly than RH. In the studies presented, 50% of IVT variability and 90% of IVS variability are explained by AH, whereas, respectively, only 12% and 36% are explained by RH. In temperate regions, both outdoor and indoor AH possess a strong seasonal cycle that minimizes in winter. This seasonal cycle is consistent with a wintertime increase in IVS and IVT and may explain the seasonality of influenza. Thus, differences in AH provide a single, coherent, more physically sound explanation for the observed variability of IVS, IVT and influenza seasonality in temperate regions. This hypothesis can be further tested through future, additional laboratory, epidemiological and modeling studies.

915 citations

Journal Article
TL;DR: The findings indicated the wide variation in the estimated number of deaths from season to season was closely related to the particular influenza virus types and subtypes in circulation.
Abstract: Influenza infections are associated with thousands of deaths every year in the United States, with the majority of deaths from seasonal influenza occurring among adults aged >or=65 years. For several decades, CDC has made annual estimates of influenza-associated deaths, which have been used in influenza research and to develop influenza control and prevention policy. To update previously published estimates of the numbers and rates of influenza-associated deaths during 1976-2003 by adding four influenza seasons through 2006-07, CDC used statistical models with data from death certificate reports. National mortality data for two categories of underlying cause of death codes, pneumonia and influenza causes and respiratory and circulatory causes, were used in regression models to estimate lower and upper bounds for the number of influenza-associated deaths. Estimates by seasonal influenza virus type and subtype were examined to determine any association between virus type and subtype and the number of deaths in a season. This report summarizes the results of these analyses, which found that, during 1976-2007, estimates of annual influenza-associated deaths from respiratory and circulatory causes (including pneumonia and influenza causes) ranged from 3,349 in 1986-87 to 48,614 in 2003-04. The annual rate of influenza-associated death in the United States overall during this period ranged from 1.4 to 16.7 deaths per 100,000 persons. The findings also indicated the wide variation in the estimated number of deaths from season to season was closely related to the particular influenza virus types and subtypes in circulation.

720 citations

Journal ArticleDOI
18 Apr 2008-Science
TL;DR: There was continuous circulation in east and Southeast Asia via a region-wide network of temporally overlapping epidemics and that epidemics in the temperate regions were seeded from this network each year, suggesting that once A (H3N2) viruses leave E-SE Asia, they are unlikely to contribute to long-term viral evolution.
Abstract: Antigenic and genetic analysis of the hemagglutinin of approximately 13,000 human influenza A (H3N2) viruses from six continents during 2002-2007 revealed that there was continuous circulation in east and Southeast Asia (E-SE Asia) via a region-wide network of temporally overlapping epidemics and that epidemics in the temperate regions were seeded from this network each year. Seed strains generally first reached Oceania, North America, and Europe, and later South America. This evidence suggests that once A (H3N2) viruses leave E-SE Asia, they are unlikely to contribute to long-term viral evolution. If the trends observed during this period are an accurate representation of overall patterns of spread, then the antigenic characteristics of A (H3N2) viruses outside E-SE Asia may be forecast each year based on surveillance within E-SE Asia, with consequent improvements to vaccine strain selection.

689 citations

Journal ArticleDOI
TL;DR: The scientific evidence for the seasonal mechanisms that potentially explain the complex seasonal patterns of influenza disease activity observed globally is examined and an analytical framework is developed that highlights the complex interactions among environmental stimuli, mediating mechanisms, and the seasonal timing of influenza epidemics.
Abstract: BACKGROUND: Despite the significant disease burden of the influenza virus in humans, our understanding of the basis for its pronounced seasonality remains incomplete. Past observations that influenza epidemics occur in the winter across temperate climates, combined with insufficient knowledge about the epidemiology of influenza in the tropics, led to the perception that cool and dry conditions were a necessary, and possibly sufficient, driver of influenza epidemics. Recent reports of substantial levels of influenza virus activity and well-defined seasonality in tropical regions, where warm and humid conditions often persist year-round, have rendered previous hypotheses insufficient for explaining global patterns of influenza. OBJECTIVE: In this review, we examined the scientific evidence for the seasonal mechanisms that potentially explain the complex seasonal patterns of influenza disease activity observed globally. METHODS: In this review we assessed the strength of a range of hypotheses that attempt to explain observations of influenza seasonality across different latitudes and how they relate to each other. We reviewed studies describing population-scale observations, mathematical models, and ecological, laboratory, and clinical experiments pertaining to influenza seasonality. The literature review includes studies that directly mention the topic of influenza seasonality, as well as other topics we believed to be relevant. We also developed an analytical framework that highlights the complex interactions among environmental stimuli, mediating mechanisms, and the seasonal timing of influenza epidemics and identify critical areas for further research. CONCLUSIONS: The central questions in influenza seasonality remain unresolved. Future research is particularly needed in tropical localities, where our understanding of seasonality remains poor, and will require a combination of experimental and observational studies. Further understanding of the environmental factors that drive influenza circulation also may be useful to predict how dynamics will be affected at regional levels by global climate change.

414 citations

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