Staff Mission Contact Us. WHO changes 2 strains for flu vaccine Filed Under :. Influenza Vaccines. Feb 22, Share this page:. Egg-adaptation problem persists The switch to a different H3N2 strain is a closely watched development, given problems with poor vaccine effectiveness that have partly been linked to egg-adaptations in the vaccine strain used to make egg-based vaccines.
New pandemic candidate virus, H7N4 findings Alongside recommending strains for upcoming flu seasons, WHO flu vaccine advisors also routinely look at zoonotic strains to see if any new candidate vaccine viruses are needed for pandemic preparedness. Sign up now». Related News All news. Sep 30 This system provides an overall indication of whether flu-associated deaths are elevated, but does not provide an exact number of how many people died from flu.
CDC estimates that from to , influenza-associated deaths in the United States ranged from a low of 12, during to a high of 79, during The model used to estimate flu-associated deaths uses a ratio of deaths-to-hospitalizations in order to estimate the total flu-related deaths during a season. As data allow, CDC will begin reporting cumulative, in-season estimates of the influenza mortality burden.
Influenza-associated deaths in children people younger than 18 became nationally reportable in Since that time the number of pediatric flu deaths reported to CDC each year has ranged from 37 season to deaths season. CDC also estimates the numbers of flu-related deaths using statistical models.
Estimates of deaths in children since have ranged from 37 to about 1, CDC believes these estimated numbers of pediatric deaths are likely a better estimate of the number of pediatric flu deaths.
There are several factors that make it difficult to determine accurate numbers of deaths caused by flu regardless of reporting. Some of the challenges in counting flu associated deaths include the following:. CDC recommends a yearly flu vaccine for everyone 6 months of age and older as the first and most important step in protecting against this serious disease.
In addition to getting a seasonal flu vaccine, you can take everyday preventive actions like staying away from sick people and washing your hands to reduce the spread of germs. If you are sick with flu, stay home from work or school to prevent spreading flu to others. In addition, there are prescription medications called antiviral drugs that can be used to treat influenza illness. Encourage your loved ones to get vaccinated.
Vaccination is especially important for people at high risk for developing flu complications , and their close contacts. Also, if you have a loved one who is at high risk of flu complications and they develop flu symptoms, encourage them to get a medical evaluation for possible treatment with flu antiviral drugs.
These drugs work best if given within 48 hours of when symptoms start. CDC recommends that people who are at high risk for serious flu complications and who get flu symptoms during flu season be treated with flu antiviral drugs as quickly as possible without waiting for confirmatory testing. People who are not at high risk for serious flu complications may also be treated with flu antiviral drugs, especially if treatment can begin within 48 hours. Some children 6 months through 8 years of age will require two doses of flu vaccine for adequate protection from flu.
Children in this age group who are getting vaccinated for the first time will need two doses of flu vaccine, spaced at least 4 weeks apart. Children who have only received one dose in their lifetime also need two doses.
Children younger than 6 months old are at high risk of serious flu complications, but are too young to get a flu vaccine. Because of this, safeguarding them from flu is especially important.
If you live with or care for an infant younger than 6 months old, you should get a flu vaccine to help protect them from flu. Advice for Caregivers of Young Children is available for more information. Everyone else who is around the baby also should be vaccinated.
Also, studies have shown that flu vaccination of the mother during pregnancy can protect the baby after birth from flu infection for several months. In addition to getting vaccinated, you and your loved ones can take everyday preventive actions like staying away from sick people and washing your hands to reduce the spread of germs. Flu vaccine is produced by private manufacturers, so supply depends on manufacturers. For the season, manufacturers projected they would provide between million and million doses of injectable vaccine for the U.
Projections may change as the season progresses. There are many vaccine options to choose from; the most important thing is for all people 6 months and older to get a flu vaccine every year. If you have questions about which vaccine is best for you, talk to your doctor or other health care professional.
While observational data from through flu seasons indicate that LAIV was not effective among 2 through year-olds against H1N1pdm09 influenza viruses in the U. Some data suggest that the new H1N1 vaccine virus included in the new LAIV vaccines will have improved effectiveness against circulating H1N1 viruses; however, no published effectiveness estimates are available yet. Getting vaccinated before flu activity begins helps protect you once flu season starts in your community.
However, getting vaccinated later can still be beneficial. CDC recommends ongoing flu vaccination as long as influenza viruses are circulating, even into January or later. Children 6 months to 8 years old who need two doses of vaccine should get the first dose as soon after vaccine is available to allow time to get the second dose before the start of flu season. The two doses should be given at least 4 weeks apart. The HealthMap Vaccine Finder external icon helps you to locate where you can get a flu vaccine.
During the — influenza season in the United States, A H1N1 pdm09 viruses were predominant in most regions early in the season [ 7 ], but from February to March , illness due to A H3N2 infections substantially increased, prompting the Centers for Disease Control and Prevention CDC to issue a health alert [ 8 ]. We assessed virologic surveillance data from public health laboratories throughout the United States, which identified increased prevalence of A H3N2 clade 3c.
To examine the epidemiologic consequences of increasing prevalence of antigenically distinct A H3N2 viruses in the United States, we analyzed data from the US Influenza Vaccine Effectiveness Flu VE Network, a multisite influenza research network that evaluates protection conferred by vaccination against influenza-associated illnesses in the ambulatory care setting. We used genetic data from viruses obtained from influenza-positive patients to calculate vaccine effectiveness VE against clade 3C.
Distribution of influenza viruses and A H3N2 clades in the United States before and during the — influenza season was examined using viruses identified at US public health laboratories from 30 September through 18 May and submitted to the CDC for virus characterization [ 7 ].
For genetic characterization, the CDC requested that state public health laboratories submit 2 influenza A H3N2 -positive specimens, 2 influenza A H1N1 pdmpositive specimens, and up to 4 influenza B—positive specimens every 2 weeks throughout the season.
Genetic characterization was used to determine genetic group and clade based on hemagglutinin sequence [ 1 ]. Details of this network have been described elsewhere [ 10 , 11 ]. Specimens were tested for influenza viruses using real-time reverse-transcriptase polymerase chain reaction RT-PCR [ 11 ].
Patients testing positive for influenza were designated as case patients, and those testing negative as noncase patients. Full-length hemagglutinin sequences were obtained by means of whole-genome sequencing from original specimen samples, performed as described elsewhere [ 12 ].
Viruses were classified into hemagglutinin clade based on phylogenetic analyses [ 13 ]. For estimates of VE, we excluded participants with inconclusive RT-PCR results, influenza-negative participants enrolled before periods of local influenza circulation, and participants vaccinated 14 or fewer days before self-reported illness onset.
For the remaining participants, we calculated descriptive statistics separately for influenza case patients and noncase patients, including medians of continuous variables and distributions of categorical variables.
Influenza VE was estimated using a test-negative design, which compares the odds of testing positive for influenza among vaccinated versus unvaccinated persons [ 14 , 15 ]. All A H1N1 pdm09 viruses genetically characterized belonged to clade 6B.
The proportion of influenza A H3N2 viruses began to increase nationally during the last week of January , and A H3N2 viruses predominated starting in the last week of February The proportion that belonged to clade 3C. Pie charts present proportional distribution of virus type or A subtype A, C or A H3N2 genetic clade B, D , based on the number of subtyped or genetically characterized influenza viruses from each region.
From 23 November through 3 May , we enrolled 10 patients seeking care for acute respiratory illness Table 1. All A H1N1 pdm09 viruses belonged to clade 6B. The proportion of clade 3C. Against A H3N2 clade 3C. ORs were estimated using logistic regression. The evasion of immunity through rapid evolution and accumulation of changes in major surface proteins of the A H3N2 virus is a challenge for influenza vaccine strain selection and production.
Since , the A H3N2 component of the northern hemisphere vaccine has been changed on 12 occasions, twice as often as the A H1N1 component, and vaccine strain selection has been postponed on 3 occasions to collect additional data on emergent A H3N2 viruses or characteristics of A H3N2 candidate vaccine viruses [ 4 ].
Although the season began with predominance of A H1N1 pdm09 viruses in most US regions, the proportion of illness caused by antigenically distinct A H3N2 viruses increased during the season, and A H3N2 was the predominant influenza virus throughout the United States after February Based on Flu VE Network data, the current analysis suggests that vaccination did not significantly reduce medically attended influenza illness due to A H3N2 virus infection.
This finding was consistent with laboratory analyses indicating antigenic difference between the — A H3N2 reference virus representing subclade 3C. The rapid increase in clade 3C. Experience from the — influenza season highlights recent challenges with VE against influenza A H3N2 viruses and the need for more broadly cross-protective vaccines [ 16 , 17 ]. Antigenic differences between egg-passaged vaccine viruses and circulating A H3N2 viruses may have contributed to reduced VE, along with other factors [ 16 , 17 ].
Reasons for increased A H3N2 activity due to clade 3C. When they first emerged, clades 3C. Continued genetic evolution of A H3N2 viruses resulted in multiple subclades of 3C. For improved VE, vaccine strategies that provide broad protection against antigenically distinct groups of A H3N2 viruses are needed if diverse groups of viruses continue to cocirculate [ 17 ].
The annual development of influenza vaccines is a challenging race against the clock to detect and monitor antigenically drifted influenza viruses, predict which viruses will predominate, and manufacture and deliver vaccines in time for each influenza season [ 2 ]. Evolving evidence on emergence and fitness of antigenically drifted viruses, trends in prevalence, and characterization of potential candidate vaccine viruses are factors that contribute to strain selection and decisions to update vaccine components.
Selection of a new vaccine reference virus can require additional manufacturing time, leading to potential public health consequences if vaccine availability is affected. Postponement of A H3N2 vaccine strain selection until 21 March , the first postponement since February , allowed collection of additional data on geographic distribution of A H3N2 clades and development of potential candidate vaccine viruses and informed the selection of a clade 3C.
Our findings of low effectiveness of — vaccines against A H3N2 -related illness became available during strain selection deliberations and supported the decision to update the vaccine. Close monitoring of A H3N2 3C. These VE estimates may also inform public health efforts to control influenza. Intraseason estimates of VE may have implications for healthcare providers.
Prompt and early antiviral treatment of high-risk and hospitalized patients with suspected influenza is particularly important when protection is suboptimal [ 22 ]. Increasing and widespread influenza activity in the United States related to A H3N2 viruses late in the — season prompted the CDC to issue a national health advisory to alert clinicians to have a high suspicion for influenza, and reinforce recommendations for antiviral treatment [ 8 ]. Several limitations of our study should be considered.
The validity of observational VE studies depends on accurate classification of vaccination status and influenza infection [ 14 ]. Vaccination status for this analysis included self-report at 4 of 5 sites, although documented vaccination status was used when available. Influenza infection was determined through systematic testing by highly specific molecular assays, and participants were enrolled within 7 days after illness onset when viral shedding was highest, decreasing the likelihood of false-negative results.
Injected trivalent inactivated influenza vaccines are most commonly used throughout the world. Influenza antigen preparation varies between manufacturers. The influenza virus characterisation reports give an overview of circulating influenza viruses in Europe.
They provide details on the current vaccine strains, summarise the development of the viruses since the last report, and closely follow the main developments for the ongoing influenza season. Vaccination is the most effective form of influenza prevention. Apart from vaccination and antiviral treatment the public health management includes personal protective measures. Weekly reports on influenza activity in Europe throughout the flu season are available as Flu News Europe reports and weekly infographic.
In the Influenza season summaries you find the ECDC main outputs during the influenza season as well as an Infographic showing a summary of the season. Vaccines represent one of the most effective and cost-saving public health intervention.
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