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Viral vaccines: Uses, common brands, and safety information

Viral vaccines help protect humans against diseases such as COVID-19, HPV, smallpox, and more

Viral vaccines protect people from becoming infected by viruses. By preventing infection in one individual, they also combat the spread of viruses to the rest of society. Thanks to viral vaccines, deadly viruses such as poliovirus, rabies virus, and variola virus (smallpox) have been eradicated or are extremely rare in the United States. However, other dangerous viruses such as hepatitis A and B are still common in the U.S., and rare viruses will become common without the continual use of viral vaccines. Global travelers also require viral vaccines to protect them from other deadly viruses such as the Yellow Fever virus.

The current COVID-19 epidemic is a somber reminder of the catastrophic effect of viruses and compels us to consider the importance of viral vaccines. Every year, approximately 50,000 adults in the United States die from diseases that could have been prevented by vaccination. People who skip vaccinations put themselves and others at risk for diseases such as shingles, flu, and hepatitis, and human papillomavirus (HPV)–some of which can even cause cancer. Viral vaccines are a preventative measure that should be a part of everyone’s health routine–just like a healthy diet, exercise, and regular check-ups.

This article will review viral vaccines available on the U.S. market; different types, how they work, and their common side effects. This article will not cover vaccines that prevent bacterial infections, such as pneumococcal, meningococcal, tetanus, or typhoid vaccines.

List of viral vaccines
Vaccine name SingleCare savings Learn more
Afluria (trivalent influenza) Get Afluria coupons Afluria details
Engerix-B (hepatitis B) Get Engerix-B coupons Engerix-B details
Fluad (adjuvanted quadrivalent influenza) Get Fluad coupons Fluad details
Fluarix (quadrivalent influenza) Get Fluarix coupons Fluarix details
Flublok Quadrivalent (quadrivalent recombinant influenza) Get Flublok coupons Flublok details  
Flucelvax (quadrivalent influenza) Get Flucelvax coupons Flucelvax details
Flumist Quadrivalent (intranasal quadrivalent influenza) Get Flumist Quadrivalent coupons Flumist Quadrivalent  details
Fluzone (quadrivalent influenza) Get Fluzone coupons Fluzone details
Fluzone High Dose (quadrivalent influenza) Get Fluzone High Dose coupons Fluzone High Dose details
Gardasil 9 (9-valent human papillomavirus) Get Gardasil coupons Gardasil details
Havrix (hepatitis A) Get Havrix coupons Havrix details
Imovax (rabies) Get Imovax coupons Imovax details
IPOL (polio) Get IPOL coupons IPOL details
Ixiaro (Japanese encephalitis) Get Ixiaro coupons Ixiaro details
M-M-R II (Measles, mumps, rubella) Get M-M-R II coupons M-M-R II details
ProQuad (Measles, mumps, rubella and varicella) Get ProQuad coupons ProQuad details
Recombivax HB (hepatitis B) Get Recombivax HB coupons Recombivax HB details
RabAvert (rabies) Get RabAvert coupons RabAvert details
RotaTeq (5-valent oral rotavirus vaccine) Get RotaTeq coupons Rotateq details
Shingrix (herpes zoster/shingles) Get Shingrix coupons Shingrix details
Twinrix (hepatitis A and B) Get Twinrix coupons Twinrix details
Vaqta (hepatitis A) Get Vaqta coupons Vaqta details
Varivax (varicella/chickenpox) Get Varivax coupons Varivax details
YF-VAX (yellow fever) Get YF-VAX coupons YF-VAX details

Other viral vaccines:

  • Janssen COVID-19 Vaccine (SARS-CoV-2)
  • Moderna COVID-19 Vaccine (SARS-CoV-2)
  • Pfizer-BioNTech COVID-19 Vaccine (SARS-CoV-2)
  • Engerix-B Pediatric (hepatitis B recombinant vaccine)
  • Ervebo (ebola viral vector vaccine)
  • Havrix Pediatric (hepatitis A inactivated vaccine)
  • Recombivax HB Pediatric/Adolescent (hepatitis B recombinant vaccine)
  • Rotarix (rotavirus live-attenuated, oral vaccine)

What are viral vaccines?

Viral vaccines protect against diseases that are caused by viruses. Some contain whole viruses that have been weakened or killed, others contain pieces of viruses called antigens. In either case, the vaccine exposes a patient to information about the virus so that their immune system can learn how to recognize it and defend itself. Viral vaccines do not cause an infection like a naturally occurring virus. They are given as an injection (into the muscle or under the skin) or taken orally.

How do viral vaccines work?

Our immune system learns how to protect us from pathogens (viruses, bacteria, and toxoids) when we encounter them in nature. Every pathogen has unique parts called antigens, which the immune system uses to distinguish one pathogen from another. The immune system remembers all the antigens it has encountered. ‘Memory cells’ are a type of immune cell that respond quickly to antigens that the body has encountered in the past. However, when a new pathogen invades the body–one that the immune system has not encountered before—it can take several days before the immune system mounts an effective attack. During this time, the pathogen can reproduce and spread rapidly inside the body, potentially causing deadly disease. Since some pathogens are extremely deadly, an infected person may die before they build up a strong immune response to the pathogen. Additionally, some pathogens mutate rapidly, which makes it harder for the immune system to recognize them during subsequent infections.

Viral vaccines teach the immune system how to attack pathogens without the patient experiencing an actual infection. In other words, they are a safer substitute for first exposure to a disease. Some vaccines contain weakened viruses that replicate very slowly. The body has time to learn how to destroy these viruses before they cause disease. Other vaccines contain modified versions of the virus that cannot replicate at all or may only contain parts of the virus called antigens. Thus, the immune system learns how to recognize these antigens and respond to them appropriately, without having to encounter a dangerous infection. The ‘valence’ of a vaccine denotes the number of antigens that the vaccine introduces to the body. A vaccine that protects against a single antigen or a single strain of a virus is called a monovalent vaccine. A vaccine that protects against multiple antigens or strains is called a multivalent vaccine. The specific valency is denoted with a prefix (e.g., a quadrivalent vaccine protects against four strains of a virus).

What are viral vaccines used for?

Viral vaccines are used to prevent infectious diseases caused by viruses. Examples include:

  • Influenza (flu)
  • Hepatitis A
  • Hepatitis B
  • Herpes zoster (shingles)
  • Human papillomavirus (HPV)
  • Japanese encephalitis (JE)
  • Measles
  • Mumps
  • Polio
  • Rabies
  • Rotavirus
  • COVID-19
  • Smallpox
  • Varicella (chickenpox)
  • Yellow Fever

Types of viral vaccines 

Live-attenuated vaccines 

Live-attenuated vaccines contain viruses that have been weakened in a laboratory. A very small amount of the virus is delivered to the patient. The virus replicates in the body to create enough of the organism to stimulate an immune response, but not enough to cause an infection. One benefit of live-attenuated vaccines is that they elicit a very strong and long-lasting immune response since the vaccine contains a form of the virus that is very similar to the naturally occurring virus. In some cases, a single dose of a live vaccine can grant lifetime protection against infection. A drawback of live vaccines is that they have the potential to cause infections in people with a weakened immune system. Patients with a weakened immune system should consult with a health care provider before receiving any live vaccines. Women who are pregnant should not be vaccinated with a live vaccine, as the fetus has not developed an adequate immune system. Centers for Disease Control and Prevention (CDC) recommends women of child-bearing potential wait four weeks after receiving a live vaccine before becoming pregnant.

Examples of live-attenuated vaccines:

  • Influenza (Flumist)
  • Measles, mumps, rubella (M-M-R-II, ProQuad)
  • Varicella (ProQuad, Varivax)
  • Yellow Fever (YF-VAX)
  • Rotavirus (Rotarix, RotaTeq)
  • Smallpox (not available on the U.S. market.)

Inactivated vaccines 

Inactivated vaccines contain viruses that have been killed through a physical or chemical process in a laboratory. When dead viruses are injected into the recipient, the immune system develops antibodies that recognize specific pieces of the virus (antigens). If the recipient ever becomes infected with the virus, the immune system will quickly recognize and destroy the virus. One advantage of inactivated vaccines over live-attenuated vaccines is that they eliminate the possibility of the virus reverting to a more infectious form. Multiple doses of an inactivated vaccine are usually required to provide a strong immune response. “Booster” doses may be required to prolong immunity.

Examples of inactivated vaccines:

  • Hepatitis A vaccine (Havrix)
  • Hepatitis A and B vaccine (Twinrix)
  • Influenza vaccine (Afluria, Fluvirin, Fluzone, Fluzone High Dose, etc)
  • Polio vaccine (IPOL)
  • Rabies vaccine (RabAvert, Imovax)
  • Japanese encephalitis vaccine (Ixiaro)

Subunit/recombinant vaccines 

Subunit vaccines use one or more parts of a virus to elicit an immune response. The specific parts of the virus that will best stimulate the immune system are called antigens. A portion of the virus’s DNA that encodes for an antigen is inserted into a bacterial or yeast cell. These cells, which now produce the antigen, are grown in a lab in large quantities as part of the manufacturing process. When subunit vaccines are produced using this strategy, they are categorized as recombinant vaccines.

Examples of subunit/recombinant vaccines:

  • Hepatitis B (Engerix-B, Recombivax HB)
  • Human papillomavirus (Gardasil 9)
  • Herpes zoster/Shingles vaccine (Shingrix)
  • Recombinant influenza vaccine (Flublok Quadrivalent)
  • Hepatitis A and B vaccine (Twinrix)

Viral vector vaccines 

Viruses, like all living organisms, contain DNA. Viruses replicate by inserting their genetic material into cells. This genetic material (either RNA or DNA) gives instructions to the cell to build proteins, which will be assembled to build a new virus. Meanwhile, the virus’s genome is replicated by an enzyme called polymerase, and the new copy of the genome is housed inside the new virus. Viral vector vaccines take advantage of this process by modifying the DNA inside a virus. Changing the DNA will change the instructions given to the host’s cell. A virus that is modified by scientists to deliver special instructions is called a viral vector. The Janssen COVID-19 vaccine uses an adenovirus viral vector, which is a non-replicating viral vector. In other words, the virus cannot create more copies of itself. Instead, it instructs the cell to make a very small piece of the SARS-CoV-2 virus. This piece (antigen) is called a spike protein, and by itself it cannot cause an infection. The immune system recognizes the spike protein as foreign and will generate antibodies trained to destroy viruses that contain this protein. After the immune system has learned to recognize and attack this signal, it will be equipped to rapidly destroy the actual SARS-CoV-2 virus if the individual ever becomes infected.

Examples of viral vector vaccines:

  • Ebola (Ervebo)
  • COVID-19 (Janssen COVID-19 Vaccine)

Messenger RNA (mRNA) vaccines

Like viral vector vaccines, mRNA vaccines deliver instructions to the host’s cells. The instructions come in the form of messenger RNA, or mRNA for short. RNA is created from DNA. Messenger RNA translates information from DNA that is directly used to build proteins. For example, the mRNA in the COVID-19 vaccines translates part of the SARS-CoV-2 virus DNA and provides information to make the SARS-CoV-2 spike protein (not the whole virus). This mRNA never enters the nucleus of the host’s cell and does not alter or interact with the host’s DNA in any way.

Examples of mRNA vaccines:

  • COVID-19 (Pfizer-BioNTech, Moderna COVID-19 Vaccines)

Who can take viral vaccines?

Infants, children, and adolescents

According to the CDC child and adolescent immunization schedule, children should receive: 

  • Three doses of hepatitis B vaccine before eighteen months of age–one at birth, a second dose between one and two months, and the third dose between six and eighteen months. 
  • Vaccination against rotavirus with Rotarix (one dose at two months, second dose at four months) or RotaTeq (first dose at two months, second dose at four months, third dose at six months). 
  • Three doses of inactivated polio vaccine (IPOL) should be given before eighteen months of age; one dose at two months, a second dose at four months, and the third dose between six and eighteen months). 
  • Annual vaccination against influenza (flu) with the inactivated influenza vaccine should begin as early as six months of age. The live-attenuated influenza vaccine can be given to children two years or older. 
  • The 2-dose series of hepatitis A vaccine (Havrix Pediatric) can begin when a child is 12 months old. Two doses should be given at least six months apart (a hepatitis A and B combination vaccine for children is not available in the United States). 
  • Human papillomavirus vaccine (Gardasil) can be given as early as nine years of age. Children who receive their first dose between nine and fourteen years require a 2-dose series, and children who get their first dose at age fifteen or older require a 3-dose series. 
  • Finally, children should begin a 2-dose series of mumps, measles, rubella vaccine (M-M-R II), and varicella vaccine (Varivax) or the combined vaccine (ProQuad) starting at twelve to fifteen months of age, with the second dose given between ages four and six years.

Currently, the CDC recommends children aged 12 years and older receive the Pfizer-BioNTech COVID-19 Vaccine.


  • Should receive an annual flu shot, either an inactivated influenza vaccine or live influenza vaccine may be administered for adults under the age of fifty. 
  • Older adults should not receive a live influenza vaccine
  • Aged fifty years or older should receive two doses of the herpes zoster vaccine (Shingrix), regardless of previous infection or previous vaccination with the herpes zoster live vaccine (Zostavax). 
  • If not vaccinated against human papillomavirus during childhood, adults should receive a three-dose series of Gardasil 9 before age twenty-seven. 
  • Those born after 1980 should receive two doses of the varicella vaccine (Varivax) if they were not vaccinated as a child. If only one dose was given as a child, a second dose should be administered as an adult. Women who are pregnant and health care personnel should be vaccinated as adults if they were not vaccinated as children, regardless of their birth year. All adults who have had a diagnosis of varicella or herpes zoster by a health care provider are considered immune and do not require vaccination
  • Those born before 1957 (other than health care personnel) do not require vaccination against measles, mumps, and rubella. Adults born after 1957 should be vaccinated with one dose of M-M-R II if they did not receive the M-M-R II or ProQuad (MMRV) vaccine during childhood. The M-M-R II and ProQuad vaccines are live vaccines and should not be administered to pregnant women, patients with a severely compromised immune system, or adults over the age of sixty-five.


The only viral vaccines indicated for adults older than 65 years are the herpes zoster and varicella vaccines. Adults can receive the two-dose series of the herpes zoster (shingles) vaccine (Shingrix) beginning at fifty years of age, regardless of previous infection or vaccination with the old shingles vaccine (Zostavax). The CDC considers people born in the U.S. before 1980 to be immune to varicella unless they are pregnant women or health care personnel.

Are viral vaccines safe?


There have been no recent recalls of vaccines in the U.S.


All marketed vaccinations are generally safe and effective when administered according to the schedules listed by the CDC. Some vaccinations are only approved for certain age groups. Vaccinations that are approved for all ages may still require doses to be administered at specific age ranges according to the CDC schedules to be safe and effective.

Contraindications to the live attenuated influenza vaccine (LAIV) Flumist include concurrent use of aspirin or aspirin-containing medication in children and adolescents. Flumist should not be administered to anyone who has taken oseltamivir or zanamivir within the past forty-eight hours, peramivir within the past five days, or baloxavir within the past seventeen days. 

Women who are pregnant should not receive the Flumist vaccine. Children 2 to 4 years old who have received an asthma diagnosis or whose health care provider has confirmed wheezing or asthma in the child during the past 12 months should not receive the Flumist vaccine. 

Persons with active cerebrospinal fluid (CSF) leaks or cochlear implants should not receive the Flumist vaccine. Persons who are immunocompromised (weakened immune system), and close contacts and caregivers of patients who are severely immunocompromised (requiring a protected environment) should not receive Flumist. Patients without a functioning spleen (i.e., sickle cell disease) should not receive Flumist.

Vaccines protecting against mumps, measles, rubella, or varicella  (i.e. M-M-R-II, ProQuad, Varivax) should not be administered to women who are pregnant, or persons with a severely compromised immune system (e.g. patients with blood or solid tumors, patients receiving chemotherapy or any long-term therapy that suppresses the immune system, patients with a congenital immune disease, or patients with HIV infection who are severely immunocompromised), or patients with a family history of altered immune function.

Vaccines protecting against hepatitis B (Recombivax HB) or human papillomavirus (Gardasil-9, Cervivax) should not be administered to patients with a yeast allergy.

Rotavirus vaccines (RotaTeq, Rotarix) should not be administered to patients with severe combined immunodeficiency (SCID) or patients with a history of intussusception. Rotavirus should be administered with caution in patients who do not have SCID but have a weakened immune system, in patients with chronic gastrointestinal disease, spina bifida, or bladder exstrophy.

All viral vaccines should be used cautiously in patients with moderate or severe acute illness with or without fever, as all viral vaccines increase the burden on the immune system.

Are viral vaccines controlled substances?

No, viral vaccines are not controlled substances.

Common viral vaccines side effects

While vaccines work to protect patients from infection, several adverse effects may occur. These are signs that the immune system is building protection. The most common side effects include:

  • Pain, redness, or swelling at the injection site
  • Headache
  • Chills
  • Fever
  • Nausea
  • Muscle pain
  • Fatigue

How much do viral vaccines cost?

Vaccine prices vary but most cost over $100 without insurance or discount programs. For example, the cash price of either rabies vaccine (Imovax and RabAvert) is over $400. Unfortunately, there are no generic versions of vaccines available at lower costs. The good news is that SingleCare can lower the cost of vaccines for patients with and without insurance. The chickenpox vaccine (Varivax) can cost nearly $250 without insurance. With a SingleCare coupon you can pay approximately $150. Flu shots can be expensive without insurance, too. The average cash price of Fluzone can be more than $100 but is less than $50 with a SingleCare savings card or coupon. 

Under the Affordable Care Act, most private insurance plans must cover certain vaccines without a copay so long as they are provided by a doctor’s office or pharmacy in their health plan’s network. Hepatitis A and B, herpes zoster, human papillomavirus, influenza, measles, mumps, rubella, and varicella vaccines are typically covered by commercial plans.

Medicare Part B covers the full cost of influenza vaccines. They also cover the cost of hepatitis B vaccines for patients at increased risk for hepatitis, and rabies vaccines if related to direct exposure to the rabies virus.

Medicare Part D must include all commercially available vaccines on their formulary, though they may charge a copay. Children enrolled in Medicaid (state insurance) receive vaccines at no cost through the Vaccines for Children program (VFC). Some Medicaid plans cover several adult immunizations, but some state plans may not cover any adult vaccines. If your insurance does not cover a vaccine-or if your insurance charges a copay- SingleCare may be able to lower your costs.

COVID-19 vaccines are free to all patients under Operation Warp Speed regardless of immigration or health insurance status. The CARES Act Provider Relief Fund covers the cost of vaccine administration for uninsured patients, otherwise, it is paid for by Medicare or commercial insurance.