How Do Inactivated Viral Vaccines Work?

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How They Work
- How do inactivated viral vaccines work?
Uses
- How are inactivated viral vaccines used?
Side Effects
- What are side effects of inactivated viral vaccines?
Drug Names
- What are names of inactivated viral vaccines?

How do inactivated viral vaccines work?

Inactivated viral vaccines are sterile biologic products that provide immunity against viral infections. Inactivated viral vaccines work by stimulating the body’s immune system to produce antibodies against specific types of viruses, and protect a person from becoming infected when exposed to these viruses.

In the case of SARS-CoV-2 coronavirus that causes respiratory illness and has led to the COVID-19 pandemic, vaccines do not entirely prevent infection but protect vaccinated individuals from serious illness and hospitalization from the disease.

Inactivated viral vaccines contain particles of proteins or genetic material from viruses. Inactivated viral vaccines may also contain substances that preserve and stabilize the vaccine, and enhance immune response. Some viral vaccines are delivered in inactivated harmless viruses such as human adenovirus.

Inactivated viral vaccines may be made from:

Surface proteins (antigens) of the viruses enable the virus to hold on to a human cell, enter inside and replicate.
Modified RNA particles (messenger RNA/mRNA) from the virus can enter host cells and induce the production of viral antigen, which stimulates an immune response from the body.
Recombined DNA material from multiple strains and subtypes of viruses, killed to eliminate disease-causing capability.

The main component of inactivated viral vaccines is the viral antigen from surface proteins, DNA, or RNA fragments against which the immune system produces antibodies. If exposed to a particular virus, the immune system recognizes the viral antigen and fights infection by preventing the virus from attaching and entering into the host cell.

Currently, inactivated viral vaccines approved by the FDA protect against viral infectious diseases that include:

Coronavirus disease (COVID-19), caused by SARS-Cov-2 virus
Hepatitis A and B virus (HAV and HBV) infections, diseases that affect the liver
Human papillomavirus (HPV) infection can lead to cervical, vaginal, vulvar, anal, and oropharyngeal cancers
Influenza (flu) is caused by multiple types/strains of influenza viruses seasonally
H5N1 influenza (Avian flu)
Japanese encephalitis virus infection, a disease that affects the brain, is spread by infected mosquitoes
Polio (poliomyelitis), a disabling disease caused by poliovirus
Rabies, caused by the rabies virus that is transmitted when bitten or scratched by rabid animals
Tick-borne encephalitis virus infection caused by a flavivirus
Herpes zoster (shingles), a painful disease caused by the varicella-zoster virus
Human immunodeficiency virus (HIV) infection that affects the immune system (pending FDA approval)

How are inactivated viral vaccines used?

Most inactivated viral vaccines are administered as intramuscular (IM) injections into the muscle. A few viral vaccines may be administered as intradermal (ID) into the skin or subcutaneous (SC) injections into the tissue under the skin.

Inactivated viral vaccines are mostly one-time series of primary and booster injections, however, influenza injections are administered every year to prevent seasonal flu. Inactivated viral vaccines approved by FDA include:

Children and adolescents

COVID-19 vaccine for:
- COVID-19 disease prevention in adolescents above age 16
- COVID-19 disease prevention - Emergency Authorization Use (EUA) in children from ages 5-15
Hepatitis A routine immunization, preexposure and postexposure prophylaxis
Hepatitis B primary immunization
Human papillomavirus vaccine, routine, and catch-up immunization
H5N1 influenza (Avian flu) immunization for individuals at increased risk of exposure
Annual flu vaccines that protect against seasonal influenza caused by multiple viral strains
Japanese encephalitis virus primary and booster vaccination for children at increased risk for exposure
Routine poliovirus vaccine prophylaxis
Rabies vaccine, preexposure and postexposure prophylaxis
Tick-borne encephalitis vaccine, primary and booster shots

Adults

COVID-19 vaccine
Hepatitis A immunization for anyone seeking protection and to those at risk for infection, preexposure and postexposure prophylaxis
Hepatitis B immunization for anyone seeking protection and to those at risk for infection
Hepatitis A and B vaccination
Routine human papillomavirus vaccine for adults up to age 26, and in special situations, for adults aged 27-45 years
H5N1 influenza (Avian flu) immunization for individuals at increased risk of exposure
Annual flu vaccines that protect against seasonal influenza caused by multiple viral strains
Japanese encephalitis virus primary and booster vaccination for individuals at increased risk for exposure
Poliovirus vaccine prophylaxis for individuals at risk for exposure
Rabies vaccine, preexposure and postexposure prophylaxis
Tick-borne encephalitis vaccine, primary and booster shots
Shingles vaccine prophylaxis
HIV vaccine administered every 3 months in conjunction with antiretroviral therapy (pending FDA approval)

What are side effects of inactivated viral vaccines?

Side effects of inactivated viral vaccines may include the following:

Injection site reactions include:
- Erythema (redness)
- Swelling
- Pain and soreness
- Tenderness and warmth
- Burning
- Pruritus (itching)
- Induration (hardening of the tissue)
- Nodule/mass
- Hematoma
- Ecchymosis/bruising
- Cellulitis
- Abscess
- Inflammation
- Edema
Headache
Myalgia (muscle pain), onset or worsening
Arthralgia (joint pain), onset or worsening
Fatigue
Malaise
Pain
Fever
Need to use fever/pain medication
Chills/shivering
Irritability
Restlessness
Drowsiness
Influenza-like illness and symptoms
Crying
Change in eating habits
Anorexia (appetite loss)
Abdominal pain or discomfort
Gastrointestinal symptoms
Nausea
Vomiting
Diarrhea
Constipation
Axillary (armpit) swelling/tenderness
Localized enlarged lymph nodes
Lymphadenopathy (swelling of lymph nodes)
Decreased/impaired mobility of the injected arm
Sore throat
Cough
Upper respiratory tract infection
Rhinorrhea (nasal discharge)
Rhinitis (inflammation of the nasal passage)
Pharyngitis (throat inflammation)
Laryngitis (inflammation of voice box)
Tonsillitis (inflammation of tonsils)
Pharyngolaryngeal pain (throat pain)
Otitis media (middle ear infection/inflammation)
Tinnitus (ringing in the ears)
Vertigo
Dizziness
Lightheadedness
Presyncope (feeling faint)
Syncope (fainting)
Flushing
Pallor
Insomnia
Lupus-like syndrome
Increase in creatine phosphokinase (CPK) levels
Tachycardia (rapid heartbeat)
Myocarditis (inflammation of heart muscle)
Pericarditis (inflammation of pericardium, the membrane around the heart)
Thrombosis (blood clot formation)
Thrombocytopenia (low platelet count)
Capillary leak syndrome (leakage of plasma from blood vessels)
Vasculitis (blood vessel inflammation)
Renal vasculitis
Henoch-Schönlein purpura (a condition that causes generalized vasculitis)
Asthma
Bronchospasm
Throat tightness
Dyspnea (shortness of breath)
Respiratory distress
Stridor (wheezing sound while inhaling)
Hypersensitive reactions such as:
- Nonspecific rash
- Urticaria (hives)
- Pruritus (itching)
- Erythematous rash (rash with redness of the skin)
- Maculopapular rash (flat lesions with raised bumps)
- Vesicular rash (rash with blisters)
- Erythema multiforme (round lesions like a bullseye)
- Allergic dermatitis
- Angioedema (swelling in the tissue under the skin or mucous membranes)
- Swelling of mouth, throat, and/or tongue
- Facial swelling
- Serum sickness (allergy-like reaction to the vaccine)
- Anaphylactic/anaphylactoid reaction (severe allergic reactions including shock)
- Stevens-Johnson syndrome (a rare medical emergency with flu-like symptoms and a painful rash)
Extensive swelling of the injected limb
Back pain
Neck pain
Pain in extremities
Muscle weakness
Arthritis (joint inflammation)
Joint swelling
Musculoskeletal stiffness
Asthenia (weakness)
Abnormal gait
Chest pain
Body aches
Feeling hot
Hyperhidrosis (excessive sweating)
Hypokinesia (slow movements)
Guillain-Barre syndrome (neurological disorder)
Paresthesia (abnormal skin sensation)
Hypoesthesia (reduced skin sensation)
Neuritis (inflammation in the peripheral nerves)
Neuropathy (nerve damage)
Neuralgia (nerve pain)
Facial paresis (impaired facial muscle movement)
Bell’s palsy (facial muscle weakness or paralysis)
Limb paralysis
Tremor
Convulsions
Febrile seizures (convulsions caused by fever)
Demyelination (loss of myelin, fatty tissue that protects nerves)
Encephalomyelitis (inflammation of brain and spinal cord)
Transverse myelitis (inflammation of spinal cord)
Encephalopathy (damage to the brain)
Encephalitis (very rare)
Meningitis (very rare)
Optic neuritis (optic nerve inflammation)
Retrobulbar neuritis (a form of optic neuritis)
Conjunctivitis (inflammation of the conjunctiva, the membrane over the whites of the eye and inner surface of eyelids)
Eye and eyelid swelling
Eye irritation, pain, and redness
Visual impairment
Photophobia (sensitivity to light)
Dysphagia (swallowing difficulties)
Dysphonia (difficulty with speech)
With tick-borne encephalitis vaccine
- Triggering of shingles in pre-exposed individuals
- Precipitation or aggravation of autoimmune disorders such as multiple sclerosis
- Hemiparesis (weakness/impaired movement in one side of the body)
- Hemiplegia (paralysis of one side of the body)
- Polyneuropathy (simultaneous damage to multiple nerves all over the body)

Information contained herein is not intended to cover all possible side effects, precautions, warnings, drug interactions, allergic reactions, or adverse effects. Check with your doctor or pharmacist to make sure these drugs do not cause any harm when you take them along with other medicines. Never stop taking your medication and never change your dose or frequency without consulting your doctor.