Influenza and Seasonal Flu Vaccines

Influenza

Influenza is a most common viral disease in the world and characterized by large-scale seasonal outbreaks. The cause of the disease is the influenza virus transmitted from person to person through the airways or contact with objects or surfaces infected with the flu virus. Every year there is an increase in seasonal sickness, which reaches a peak in the winter.

The disease may be characterized by fever, muscle aches, headaches, coughing, diarrhea, weakness and general bad feeling. The symptoms are sharper than those of a common cold, and may also be accompanied by sore throat, inflammation of the eyeballs, and increased lymph nodes in the neck. The symptoms of the flu are disturbing and unpleasant, but they go away most often after a few days or nearly a week. The problem of the disease as opposed to other viruses mainly in its possible complications, including complications from pneumonia, bronchitis, ear infections, nervous system complications, and flare-ups of background diseases.

Types of influenza

There are 3 types of RNA viruses that cause influenza type A, B and C.

Human influenza type A and B, the so called “ flu “, causes annual epidemics with symptoms like sniffling, aching, coughing, and running high fevers.

Type A influenza viruses are capable of infecting animals as well. This type of virus is changing and can cause large flu epidemics and is spread by people who are already infected.

Influenza A viruses are divided into subtypes based on two proteins on the surface of the virus: the hemagglutinin (H) and the neuraminidase (N). There are 18 different hemagglutinin subtypes and 11 different neuraminidase subtypes. (H1 through H18 and N1 through N11 respectively.)

Influenza A viruses can be further broken down into different strains.

Different strains of the flu virus mutate over time and replace the older strains of the virus, that’s why it’s recommended to get a flu shot each year to ensure that your body develops immunity to the new strains of the viruses. Current subtypes of influenza A viruses found in people are influenza A (H1N1) and influenza A (H3N2) viruses. In the spring of 2009, a new influenza A (H1N1) virus (CDC 2009 H1N1 Flu website) emerged to cause illness in people. This virus was very different from the human influenza A (H1N1) viruses circulating at that time. The new virus caused the first influenza pandemic in more than 40 years. That virus (often called “2009 H1N1”) has now replaced the H1N1 virus that was previously circulating in humans.

Type B virus is found only in humans and can cause less reaction and does not cause pandemics, but still can be harmful. Influenza B viruses are not divided into subtypes, but can be further broken down into lineages and strains.

Influenza C viruses are also found in people. People generally do not become very ill from the influenza type C viruses. And this type of viruses does not cause epidemics.

 

Who is at risk?

Influenza can affect anybody, but certain groups are at increased risk:

Children aged 6 months to 12 years

Adults over the age of 50

Pregnant women, women who plan pregnancy or after childbirth

People of any age suffering from long-term illnesses such as diabetes, heart disease, lung disease, kidney disease, liver disease, blood, metabolic, or neurological diseases,

People who have been hospitalized with the flu, flu-like illness, or previous pneumonia.

Preventing Seasonal Flu

One of the important steps in preventing the flu is to get a flu vaccination each year. CDC studies show that getting a vaccination reduces risk of hospitalizations and disease complications. CDS also recommends everyday preventive actions (like staying away from people who are sick, covering coughs and sneezes and frequent handwashing) to help slow the spread of germs that cause respiratory (nose, throat, and lungs) illnesses, like the flu.

Influenza vaccination

Influenza vaccination is the most effective way to prevent the disease. Studies by the leaders of the National Program for Quality Indicators in the Community shows that the higher the rate of immunization in the population, the lower the rate of hospitalization for influenza and its complications.

Types of Vaccines

CDC recommended the use of injectable influenza vaccines (including inactivated influenza vaccines and recombinant influenza vaccines) during 2017-2018. Both trivalent (three-component) and qTrivalent flu vaccines include:

• Standard-dose trivalent shots (IIV3) that are manufactured using viruses grown in eggs. Different flu shots are approved for different age groups. Most flu shots are given in the arm (muscle) with a needle. One trivalent vaccine formulation can be given with a jet injector, for people aged 18 through 64 years.
• A high-dose trivalent shot, approved for people aged 65 and older.
• A recombinant trivalent shot that is egg-free, approved for people 18 years and older, including pregnant women.
• A trivalent flu shot made with adjuvant (an ingredient of a vaccine that helps create a stronger immune response in the patient’s body), approved for people 65 years of age and older.

Quadrivalent flu vaccines include:

• Quadrivalent flu shots approved for use in different age groups, including children as young as 6 months.
• An intradermal quadrivalent flu shot, which is injected into the skin instead of the muscle and uses a much smaller needle than the regular flu shot. It is approved for people 18 through 64 years of age.
• A quadrivalent flu shot containing virus grown in cell culture, which is approved for people 4 years of age and older.
• A recombinant quadrivalent flu shot approved for people 18 years of age and older, including pregnant women (new this season).

How do flu shots work

Flu vaccines that contain viruses cause the development of antibodies, helping the immunity to imitate the infection. The vaccine itself doesn’t cause the flu, but does take about two weeks to start working.

Traditional flu vaccines (called “trivalent” vaccines) are made to protect against three flu viruses; an influenza A (H1N1) virus, an influenza A (H3N2) virus, and an influenza B virus.

The flu virus changes every year:

One of the biggest problems with the flu virus is that each year the virus changes. Unlike other diseases, which after infection cause the body to produce antibodies and prevent further infection, the flu virus changes each year and does not allow the body long-term defense against it.

For this reason, vaccine manufacturers make up a new vaccine each year according to estimates of virus changes, so one must be re-vaccinated each year.

Do flu shots have side effects?

The most common side effect of the flu shot is the reaction at the injection side. Some redness or slight swelling can appear. These effects disappear after a few days. Some can experience headaches or pains in the muscles. Less common side effect that can appear in some people is slight fever.

All these effects go away after 2-3 days.

What are the benefits of flu vaccination?

• Flu shots can keep you from getting sick with the flu.
• Flu vaccination can reduce the risk of flu-associated hospitalization among all populations.
• Flu vaccination is an important preventive tool for people with chronic health conditions..
• Vaccination helps protect women during and after pregnancy.
• Flu vaccination may also make your illness moderate if you do get sick.
• Getting vaccinated yourself also protects people around you.

 

References:

• Prevention and Control of Seasonal Influenza with Vaccines: Recommendations of the Advisory Committee on Immunization Practices (ACIP), 2009

 

Anthony E. Fiore, David K. Shay, Karen Broder, John K. Iskander, Timothy M. Uyeki,        Gina    Mootrey,  Joseph S. Bresee and Nancy J. Cox

Morbidity and Mortality Weekly Report: Recommendations and Reports

Vol. 58, No. 8 (July 31, 2009), pp. 1-52.