Influenza A Virus Vaccine H1N1 Inactivated (Intramuscular)


Influenza is a viral infection of the lungs, throat and bronchial tubes. Common symptoms of infection include muscle aches, pains in the arms/back/legs, headaches, coughing, fever and/or chills. Certain demographics (such as geriatric patients, pediatric patients, and those who are weakened by other medical conditions or diseases) are at risk of becoming seriously ill if they contract the flu virus. Consequently, thousands of people die every year either as a direct or indirect result of flu infection.

Because of this risk, many patients elect to receive the influenza A virus vaccine. This vaccine works by introducing an inactive version of the virus into the body. This causes the body to produce its own antibodies against the infection, therefore preparing the body to be able to fight off the real, live version of the illness.

The H1N1 strain of influenza is often referred to as 'œswine flu', which received its name as many people who caught it in the past had worked or lived in and around pigs ' although today, modern strains of the illness are reported all over the world. The same influenza virus vaccine for standard strains of the disease can also be effective in treating the H1N1 strain.

Type Of Medicine

  • Vaccine

Conditions Treated

  • Influenza type A (H1N1)

Side Effects

Like most medicines, the influenza A virus vaccine (H1N1, inactivated) can cause unwanted side effects along with its desired effects. The most commonly reported side effects by patients who have received this vaccination include the following:

  • Fever
  • Joint pain
  • Muscle stiffness
  • Aches and cramps
  • Swollen joints
  • A general feeling of illness or discomfort
  • Difficulty moving
  • Joint pain

These side effects are most likely to appear a day or two after receiving the influenza vaccine. It should take another day or two for most (if not all) of these symptoms to lessen or disappear completely. If these or other symptoms persist over a prolonged period or appear to get worse, the patient is advised to follow this up with his or her doctor as soon as possible. In some cases, a doctor or pharmacist may be able to recommend ways to alleviate these temporary side effects using over the counter remedies or complimentary medicines.

Most patients will typically only experience very minimal side effects after receiving the H1N1 influenza vaccine, if they observe any symptoms whatsoever. The vaccine is intended to prevent the previously mentioned symptoms occurring on a greater scale were the patient to contract the live flu virus, and as such it is generally prescribed to at-risk patients because the benefits of preventing infection with influenza A (H1N1) far outweigh the risks of experiencing side effects which cause mild discomfort.

Other side effects, which are experienced much less frequently ' albeit often enough to warrant mentioning ' include the following:

  • Back pain
  • Tarry, black stools
  • Blindness
  • Bleeding gums
  • Blisters on the skin
  • Blood in the stools or urine
  • Color blindness
  • Blurry vision
  • Numbness, itching, tingling or prickling sensations
  • Chills
  • Coughing
  • Diarrhea
  • Difficulty breathing
  • Difficulty swallowing
  • Dizziness
  • Dry or sore throat
  • Pain in the eyes
  • Fainting
  • Increased heart rate
  • Increased temperature
  • Headache
  • Flushing of the face and neck
  • Hives
  • Muscular weakness
  • Swelling of the eyelids, face, lips and/or tongue
  • Red skin lesions
  • Runny nose
  • Pins and needles
  • Skin rash
  • Sneezing
  • Ulcers, sores or white spots on the lips or in the mouth
  • Tender, painful or swollen lymph glands in the armpit, groin or neck
  • Tightness in the chest
  • Changes in voice
  • Wheezing

Not all side effects may have been reported or listed. Patients who think they may have experienced an unreported side effect should consult their doctor and report their findings to the FDA.


The influenza A virus vaccine (H1N1, inactivated) should only be administered by a qualified physician, at the standard dose. This means that adult patients should typically only receive a singular dose in any one season/year.

Vaccine dose sizes can vary dependent on the patient's individual statistics. The manufacturers of the influenza A virus vaccine (H1N1, inactivated) provide general dosage instructions, although it should be reiterated that these are guidelines which can be altered at the discretion of the administering doctor. Factors discussed between patient and doctor will generally influence the dose size. Most doctors will consider the age, height, weight, condition and risk level of the patient when establishing the correct vaccine size.

The usual adult dose for prophylaxis against the flu virus is 0.5mL of the influenza A virus vaccine (H1N1, inactivated), intramuscularly. The patient need only receive this injection once.

For children aged 6 to 35 months of age, the standard dose is two 0.25mL intramuscular injections of the vaccine, given approximately one month apart.

Children aged 36 months to 9 years should receive two 0.5mL intramuscular injections of the flu vaccine, approximately one month apart.

Children above the age of 10 can be vaccinated with the standard adult dose (0.5mL, once).

Patients are warned against receiving any more doses of the vaccine than they require. Receiving more flu shots than required will not protect the patient any further and can even cause complications including more severe side effects or symptoms of overdose. Patients who experience signs of overdose after taking this or any other medicine may require immediate medical attention and should contact their local poison control center on 1800-222-1222 or emergency services on 911.


All drugs and vaccines have the potential to interact with other medicines or chemicals within the human body. These interactions can in some cases cause one or more medicines to become ineffective in treating the condition they were prescribed to alleviate. In other instances, interactions can cause serious or even fatal side effects. Because of these risks, patients are advised to keep a full and detailed list of all medicines they are currently undergoing treatment with. This applies to over the counter remedies, vitamins, herbal supplements and complimentary medicines as well as prescription medications.

Below is a partial list of drugs known to interact negatively with the influenza A virus vaccine (H1N1, inactivated). Patients who are currently taking one or more of these medications should inform their doctor or healthcare provider prior to receiving the flu vaccine:

  • Vinorelbine
  • Vincristine Liposome
  • Vincristine
  • Vinblastine
  • Venetoclax
  • Vedolizumab
  • Trimetrexate
  • Trimetrexate
  • Triamcinolone Ophthalmic
  • Triamcinolone Ophthalmic
  • Triamcinolone
  • Triamcinolone
  • Trastuzumab
  • Trastuzumab
  • Trabectedin
  • Trabectedin
  • Tositumomab
  • Tositumomab
  • Topotecan
  • Topotecan
  • Tofacitinib
  • Tofacitinib
  • Tocilizumab
  • Tocilizumab
  • Tisagenlecleucel
  • Tipiracil / Trifluridine
  • Thiotepa
  • Thioguanine
  • Thalidomide
  • Teriflunomide
  • Teniposide
  • Temsirolimus
  • Temozolomide
  • Tacrolimus
  • Procarbazine
  • Prednisone
  • Prednisolone
  • Pralatrexate
  • Ponatinib
  • Pomalidomide
  • Plicamycin
  • Pentostatin
  • Pemetrexed
  • Pazopanib
  • Panobinostat
  • Palbociclib
  • Paclitaxel Protein-Bound
  • Paclitaxel
  • Olaratumab
  • Ofatumumab
  • Ocrelizumab
  • Obinutuzumab
  • Midostaurin
  • Methylprednisolone
  • Methotrexate
  • Mercaptopurine
  • Melphalan
  • Mechlorethamine
  • Letrozole / Ribociclib
  • Lenalidomide
  • Leflunomide
  • Infliximab
  • Imatinib
  • Ifosfamide / Mesna
  • Ifosfamide
  • Idelalisib
  • Idarubicin
  • Ibrutinib
  • Ibritumomab
  • Guselkumab
  • Golimumab
  • Gemtuzumab
  • Gemcitabine
  • Fludarabine
  • Floxuridine
  • Fingolimod
  • Eribulin
  • Epirubicin
  • Elotuzumab
  • Efalizumab
  • Deflazacort
  • Decitabine
  • Daunorubicin Liposomal
  • Daunorubicin
  • Dasatinib
  • Daratumumab
  • Dactinomycin
  • Daclizumab
  • Dacarbazine
  • Clofarabine
  • Cladribine
  • Cisplatin
  • Chlorambucil
  • Certolizumab
  • Carmustine
  • Carfilzomib
  • Carboplatin
  • Capecitabine
  • Canakinumab
  • Cabazitaxel
  • Blinatumomab
  • Bleomycin
  • Bexarotene
  • Betamethasone
  • Bendamustine
  • Belinostat
  • Belimumab
  • Belatacept
  • Basiliximab
  • Altretamine
  • Alemtuzumab
  • Alefacept
  • Aldesleukin
  • Adalimumab
  • Acalabrutinib
  • Abemaciclib
  • Abatacept


Patients with severe allergies to poultry and/or chicken eggs should avoid receiving this vaccination. This is because eggs are used in the incubation and manufacturing processes of this vaccine.

If the patient has experienced Guillain-Barré Syndrome, a type of infection found in the vagina or rectum, within 2 months of any previous flu vaccine, administration of this influenza virus vaccine (H1N1 inactivated) must be taken with caution, with great consideration given to any potential risks and benefits of receiving the vaccine this time around.

Patients who are immunocompromised may have a diminished immune response to the influenza virus vaccine (H1N1, inactivated).

The safety and efficacy of this vaccine has not been established in pregnant women or breastfeeding mothers. Patients who are pregnant or intending on becoming pregnant soon should discuss this with their doctor. Breastfeeding mothers may wish to cease breastfeeding for a short period directly after receiving the vaccine, or to omit receiving the vaccine in favor of continued breastfeeding.

Some patients may experience adverse reactions at the site of injection. The most commonly-reported reactions were pain, redness, tenderness and swelling. Some patients also reported muscle aches for an extended period, not exceeding one week.


The influenza A virus vaccine (H1N1, inactivated) is generally administered in a clinical setting, which means the patient's healthcare provider is responsible for its safe storage. However, it may also be administered in the patient's home, or in public places such as workplaces or educational facilities.

The vaccine should be kept refrigerated (between 2C and 8C), although it should never be allowed to reach freezing temperatures. Flu vaccine storage should be overseen by qualified professionals, which means the vaccine should be stored away from access to the general public.


While the influenza A virus vaccine (H1N1, inactivated) is greatly beneficial, it can also pose a risk to patients who do not communicate effectively with their physicians. It is designed to prevent at-risk patients from becoming infected with the flu virus, but it can also cause many uncomfortable temporary side effects including dizziness, muscular pain, runny nose, fever, coughing and other flu-like symptoms. These side effects can impair the day-to-day functioning of the patient and even place them in potentially perilous situations if the correct precautions are not taken. There are also hundreds of medicines which can potentially interact with the flu vaccine, which can put the patient at further risk.

For these reasons, it is important for the patient to be honest and forthcoming about as much of their own medical information as possible, including any hereditary illnesses or diseases prevalent in the family.

When taken correctly, the influenza A virus vaccine (H1N1, inactivated) can prevent an at-risk patient from contracting the illness, which can be debilitating or even fatal in certain groups, such as the elderly. To achieve this, both patient and doctor must work together to establish whether the patient will benefit from the vaccine, and whether it is safe for them to receive it.