Influenza - Vaccine, Symptoms & Prevention

What is influenza (Flu) and how is it caused?

Influenza is a highly contagious respiratory viral illness. Each year, approximately 2800 Australians die directly from the seasonal flu, complications due to the flu, or pneumonia. Influenza A and B are the major types of viruses that infect many parts of the body, including lungs. Influenza is an airborne virus and is transmitted by sneezing, coughing, and talking.

What are the symptoms of influenza?

Persons with influenza may have symptoms including a fever, cough, sore throat, fatigue, muscle aches, headaches, runny nose and watery eyes. Children may experience vomiting and diarrhoea in addition to these symptoms. Although the fever and body aches usually last for 3-5 days, a cough and fatigue may persist for 2 weeks or more.

How long is a person with influenza contagious?

The period between infection and onset of symptoms (incubation period) for influenza is 1 to 4 days. A person with influenza may be contagious for 3-7 days after the onset of symptoms. Children may be contagious for longer than 7 days.

How can influenza and its complications be prevented?

Influenza can be prevented with a high degree of success when a person receives the current influenza vaccine. These vacinations remain the the single most effective form of prevention in spreading the flu in the community. The vaccine is made each year so that it contains the influenza strains that are expected to cause illness in that year.

Is the influenza vaccine safe?

The vaccine does not cause influenza. It does not contain 'live virus'. Generally, people have no reaction to the vaccine. Some people may experience mild side effects such as tenderness and redness at the injection site. These side effects usually clear within a day.

Persons with allergies to eggs or chicken products should talk to their immunisation provider prior to vaccination, as it is prepared from influenza viruses grown in eggs.

How effective is influenza vaccine?

In years in which there is a good match between the vaccine virus and the virus strain causing illness, influenza vaccine is generally considered to be 70%-90% effective in preventing influenza illness in healthy adults. It is important to know that it takes about 2 weeks after influenza vaccination for a person to develop protection against influenza infection. Also, influenza vaccine does not protect against respiratory illness caused by other viruses.

Can you get influenza from a vaccination?

No, it is absolutely impossible to get influenza from the vaccine. The viruses in the vaccine are inactivated and incapable of causing influenza. Instead, the person is protected from influenza by antibodies that are formed by the immune system's response to the vaccine. The amount of antibodies in the body is greatest 1 or 2 months after vaccination and then gradually declines. For that reason and because the influenza viruses usually change each year, a high-risk person should be vaccinated each autumn with the new vaccine.

Which strains have been included in this year's vaccine for Australia?

The Australian vaccine for the year 2011* contains:

• A (H1N1) : an A/California/7/2009 (H1N1) — like virus
• A (H3N2) : an A/Perth/16/2009 (H3N2) — like virus
• B : a B/Brisbane/60/2008 — like virus

*As approved by the World Health Organization (WHO) and the Australian Influenza Vaccine Committee (AIVC) on Influenza Vaccines (published by the Therapeutic Goods Administration on 13 October 2010).

Is influenza considered serious?

For healthy children and adults, influenza is typically a moderately severe illness. Most people are back on their feet within a week. For people who are not healthy or well to begin with, influenza can be very severe and even fatal. Symptoms have greater impact on these people and complications can occur. Most of these complications are bacterial infections because the body can be severely weakened by influenza such that its defences against bacteria are low. Bacterial pneumonia is the most common complication of influenza. Also, the sinuses and inner ears may become inflamed and painful.

Who gets influenza?

Anyone can get influenza, especially when it is widespread in the community. People who are not healthy or well to begin with are particularly susceptible to the complications that can follow. For anyone in a high risk category, influenza is a very serious and potentially fatal illness.

The National Health and Medical Research Council recommend annual vaccination

General:

• All adults aged 65 years and over.
• All Aboriginal and Torres Strait Island adults aged 50 years and over.

For individuals who are at increased risk of influenza-related complications:

• Adults and children (aged 6 months and over) with chronic disorders of the pulmonary or circulatory systems. This includes children with congenital heart disease and cystic fibrosis. Annual vaccination is also recommended for severe asthmatics, such as those requiring frequent hospitalisation.
• Adults and children (aged 6 months and over) with other chronic illnesses requiring regular medical follow-up or hospitalisation in the preceding year. This includes diabetes mellitus (and other chronic metabolic diseases), renal dysfunction, haemoglobinopathies, or immunosuppression caused by medication.
• Residents of nursing homes and other long-term care facilities.
• Children and teenagers (aged 6 months to 18 years) on long-term aspirin therapy who may therefore be at risk of developing Reye syndrome after influenza.

For those who can transmit influenza to person at increased risk:

• Health care providers, staff of nursing homes and other long-term care facilities.
• Providers of home care to persons at high risk.
• Household members of persons of increased risk groups.

For other groups:

• Pregnant women who fall into one of the above risk categories should be vaccinated.
• All women who will be in the second or third trimester of pregnancy during the influenza season should be vaccinated in advance.
• Influenza vaccination is recommend for HIV infected persons.
• Any person in the above risk groups should be vaccinated against influenza prior to travel. In addition, any person travelling to the Northern Hemisphere from October to March should consider influenza vaccination prior to departure.