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The Influenza vaccine: part 2
Updated: 03-Sep-2010
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When spread by droplets or direct contact, the flu virus, if not killed by the host’s immune system, replicates in the respiratory tract and damages host cells.
In people who are immuno-compromised, the virus can cause viral pneumonia or stress the individual’s system to such an extent that they become more susceptible to bacterial infections, especially bacterial pneumonia.
Groups at increased risk of conventional/seasonal influenza complications include:
• People aged 65 years or older
• Residents of nursing homes and other chronic-care facilities housing patients of any age who have chronic medical conditions;
• Adults and children with chronic disorders of the pulmonary, cardiovascular, or immune systems, including children with asthma;
• Adults and children who have required regular medical follow-up or hospitalization during the preceding year because of chronic metabolic diseases (including diabetes mellitus), renal dysfunction, hemoglobinopathies, or immunosuppression (including immunosuppression caused by medications);
• Children and teenagers (six months to 18 years of age) who are receiving long-term aspirin therapy and therefore may be at risk of developing Reye syndrome after influenza;
• Women in the third trimester of pregnancy or in the early postpartum period. There is some evidence to suggest that women who are in the third trimester of pregnancy or in the early postpartum period may be at increased risk for serious medical complications after influenza infection.
Furthermore, it is advisable that all children six to 59 months of age get a yearly conventional flu vaccination since each year there are many children who require hospitalisation because of the flu, which is easily passed from child to child.
In addition, the following groups should be vaccinated because they may transmit influenza to people who are at high risk for complications if they become infected with either the conventional or novel H1N1 flu.
• Physicians, nurses, and other health-care personnel in both hospital and outpatient-care settings
• Employees in nursing homes and chronic-care facilities who have contact with patients or residents
• Providers of home care to people at high risk (for example, visiting nurses and volunteer workers)
• Household members (including children) of high-risk people
Finally, the flu vaccine may be administered to any person who wishes to reduce his or her chances of acquiring influenza infection. People who provide essential community services should be considered for vaccination to minimize disruption during influenza outbreaks.
Students or other people in institutional settings, such as those who reside in dormitories, should be encouraged to receive the vaccine to minimize the disruption of routine activities during epidemics. The only people who should not have the vaccination are those who are allergic to eggs as these are used as the culture medium to produce the vaccine or if there is a known allergic reaction to the vaccine in previous years.
Unfortunately, because the novel 2009 H1N1 flu virus did not follow the conventional flu pattern for time of disease appearance (it appeared in April and increased over the summer and autumn of 2009), or the usual susceptible populations, recommendations for vaccination have been altered this year.
Groups at increased risk of novel H1N1 influenza complications include:
• Pregnant women,
• People who live with or care for children younger than six months of age,
• Health-care and emergency-services personnel,
• People between the ages of six months through 24 years of age and children five to18 years of age who have chronic medical problems,
• People from 25-64 years of age who are at higher risk for novel H1N1 because of chronic health disorders or compromised immune systems.
Although annual Influenza (injectable) vaccination has long been recommended for people in the high-risk groups, many still do not receive the vaccine, often because of their concern about side effects. They mistakenly perceive Influenza as merely a nuisance and believe that the vaccine causes unpleasant side effects or that it may even cause the flu. However, injectable Influenza vaccine has never been capable of causing Influenza because it consists of a killed virus.
Some people do not receive Influenza vaccine because they believe it is not very effective. There are several different reasons for this belief. People who have received Influenza vaccine may subsequently have an illness that is mistaken for Influenza, and they believe that the vaccine failed to protect them. These symptoms which include mild fever and cold-like symptoms are often simply an immune-response reaction.
Overall, vaccine effectiveness varies from year to year, depending upon the degree of similarity between the Influenza virus strains included in the vaccine and the strain or strains that circulate during the influenza season. Because the vaccine strains must be chosen nine to 10 months before the Influenza season, and because Influenza viruses mutate over time, sometimes mutations occur in the circulating virus strains between the time the vaccine strains are chosen and the next influenza season ends.
These mutations sometimes reduce the ability of the vaccine-induced antibody to inhibit the newly mutated virus, thereby reducing vaccine efficacy. This commonly occurs with the conventional flu vaccines as the specific virus types chosen for vaccine inclusion are based on reasoned projections for the upcoming flu season.
Occasionally, the vaccine does not match the actual predominating virus strain and is not very effective in generating a specific immune response to the predominant infecting flu strain, resulting in people still becoming infected with the Influenza virus despite vaccination against it.
Influenza season 2010-11
On August, 10, the director general of WHO, Dr Margaret Chan, said H1N1 has now moved to a post-pandemic period and that the novel H1N1 virus has largely run its course.
As we enter the post-pandemic period, this does not mean that the H1N1 virus has gone away. Based on experience with past pandemics, it is expected that the H1N1 virus will take on the behaviour of a seasonal influenza virus and continue to circulate for some years to come.
Globally, the levels and patterns of H1N1 transmission now being seen differ significantly from what was observed during the pandemic. Out-of-season outbreaks are no longer being reported in either the northern or southern hemisphere. Influenza outbreaks, including those primarily caused by the H1N1 virus, show an intensity similar to that seen during seasonal epidemics.
During the pandemic, the H1N1 virus crowded out other influenza viruses to become the dominant virus. This is no longer the case. Many countries are reporting a mix of influenza viruses, again as is typically seen during seasonal epidemics.
If you would like further information regarding the use and availability of the Influenza vaccine please come and talk to us. Luzdoc will be stocking the Influenza vaccination, which will have the three vaccine viruses that are recommended for 2010/2011, from September.
Best health wishes,
THE LUZDOC TEAM
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