Varicella Epidemiology In Canada
In the pre-vaccine era, approximately 350,000 varicella cases were estimated to occur each year in Canada. However, assessing the effect of varicella immunization programs on the incidence of varicella is difficult because varicella infections are significantly under-reported, less than 10% of the expected cases being reported through the Canadian Notifiable Disease Surveillance System annually.
A review of data from the Canadian Institute for Health Information for 1994 to 2000 showed that over 1,550 varicella hospitalizations occur annually for all age groups. Information on pediatric hospitalized cases and deaths are available from the Immunization Monitoring Program, ACTive for the periods 1990 to 1996 and 1999 to 2009. These data indicate that the majority of hospitalizations occur in previously healthy children. For the most recent period, 1999 to 2009, a total of 2,297 pediatric varicella related hospitalizations were reported from 12 sites across Canada, averaging 208 hospitalizations annually for children age up to 16. Among these cases, children at pre-school ages were affected mostly and accounted for 14% and 66% of the total hospitalizations, respectively. Since the public funded vaccine programs began in 2004 in Canada, the annual hospitalizations of varicella dropped from 288 to 114 .
Who Should Get The Chickenpox Vaccine
The chickenpox vaccine is a routine childhood vaccination recommended for all children. The Advisory Committee on Immunization Practices recommends that all healthy people get the vaccine. The only exception would be for people who have evidence of immunity, which can include:
- Having lab results confirming immunity or infection
- A diagnosis of chickenpox or herpes zoster from a healthcare provider
People born before the year 1980 are considered to have immunity, with the exception of those who are immunocompromised, pregnant, or work in a healthcare setting.
One version of the vaccine may be given if someone suspects they may have been exposed to chickenpox as postexposure prophylaxis to reduce the risk of infection. This is recommended for unvaccinated, healthy people 12 months or older who do not have evidence of immunity to prevent the disease. For maximum effectiveness, it must be administered within five days after exposure.
Who Shouldnt Get The Chickenpox Vaccine
You should not be vaccinated against chickenpox if you:
- Are moderately to severely ill at the time of vaccination
- Are pregnant
- Have ever had an allergic reaction to gelatin, the antibiotic neomycin, or a previous dose of chickenpox vaccine
- Are an organ donor recipient
These people should check with their doctor about getting the chickenpox vaccine:
- Patients undergoing chemotherapy or radiation for cancer
- People taking steroid drugs or other immunosuppressants
- People with HIV or another disease that compromises the immune system
- Patients who recently had a blood transfusion or received other blood products
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If The Virus In Chickenpox Vaccine Is Live Can It Cause Chickenpox
About 2% of the children who are vaccinated develop a very mild case of chickenpox, usually with no more than five to six blisters.
It is also possible for a person who has been vaccinated for chickenpox to develop chickenpox at some later point in life. When that happens, the disease is almost always milder and the recovery more rapid than for people who have not had the shots. The lesions also may not follow the same crusting pattern and the vesicles may not have as much fluid in them when a vaccinated patient develops the virus.
But it’s important to keep in mind that up to 90% of the people who get the vaccine will not catch chickenpox.
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Prevention With The Chickenpox Vaccine

Before the chickenpox vaccine was made available in 1995, the infection was common. In the early 1990s, about 4 million people were diagnosed, more than 10,000 were hospitalized, and 100150 people died each year due to chickenpox. The vaccine is now widely available and has prevented 3.5 million people from becoming infected, 9,000 from being hospitalized, and 100 people from dying each year.
There are two chickenpox vaccines approved for use in the United States:
- ProQuad: This version is a combination vaccine. It contains the measles, mumps, rubella, and chickenpox vaccines. It is approved for use in children between the ages of 12 months and 12 years.
- Varivax: This is a chickenpoxonly vaccine that is approved for use in adults, adolescents, and children who are 12 months and older.
Both chickenpox vaccines are administered in two doses.
When used to prevent chickenpox , the timing of the doses depends on at what age you received the first dose. Babies who get the first dose of the vaccine when they are between 12 months old and 15 months old will get a second shot between the ages of 4 and 6 years old.
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How Do You Get Chicken Pox
Chicken pox is extremely contagious. It spreads very quickly from person to person. The most common way the infection is spread is through the air if someone with chicken pox coughs or sneezes. You can also get chicken pox if you touch a blister or the liquid from a blister.
A pregnant woman with chicken pox can pass it on to her unborn baby before birth. Mothers with chicken pox can also give it to their newborn baby after birth.
Children Younger Than 13 Years Of Age
A routine two-dose varicella vaccine policy was recommended in the United States in 2007 .553 All healthy children should receive two 0.5-mL doses of a varicella-containing vaccine administered subcutaneously. The recommended ages for administering the first and the second doses of MMR and varicella vaccines are harmonized however, the second varicella vaccine dose may be administered at an earlier age if the interval between the first and second doses is at least 3 months. For the first dose vaccination at age 12 to 47 months, MMR vaccine and monovalent varicella vaccine or MMRV vaccine may be used. Because of the increased risk of febrile seizures following MMRV vaccine compared with MMR and monovalent varicella vaccines administered at the same visit , the CDC recommends that MMR vaccine and monovalent varicella vaccine be administered for the first dose in this age group, unless the parent or caregiver expresses a preference for MMRV vaccine. If the first dose is administered at age 48 months or older, and also for the second dose at any age, use of MMRV vaccine is preferred over separate injections of its equivalent component vaccines .667
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Who Should Not Have The Chickenpox Vaccine
- Babies less than 1 year old.
- People with weak immune systems and/or people who are taking drugs to suppress their immune system.
- Those who are pregnant. The chickenpox vaccine contains a very weak form of the virus and such vaccines are generally not recommended in pregnancy because of concern that the vaccine may be passed to the fetus. However there has been no harm to the babies born to mothers who got this vaccine during pregnancy.
- People who have had a serious allergic reaction to a previous dose of the vaccine should not get it again unless seen by a specialist and vaccinated in a special clinic that can control serious reactions.
What Are Reasons I Should Wait To Get The Chickenpox Vaccine
- You are sick or have a fever.
- You are a pregnant woman. Wait to get the vaccine until after you give birth. If you are trying to get pregnant, wait until your healthcare provider says it is okay to get the vaccine.
- You take antiviral medicine. You will need to stop the medicine and wait at least 1 day before you get the chickenpox vaccine. Examples of antiviral medicines include acyclovir and valacyclovir.
- You got a smallpox vaccine. Wait at least 4 weeks before you get the chickenpox vaccine.
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Who Should Have The Chickenpox Vaccine
It is recommended for certain individuals, such as:
- non-immune healthcare workers
- people who come into close contact with someone who has a weakened immune system
This is to lower the chances of infecting people at risk. For example, if you’re having chemotherapy treatment, it’s advisable that non-immune children close to you are given the chickenpox vaccine.
The vaccine would also be recommended if you were about to start work in a radiotherapy department and had not had chickenpox before.
How Is Chickenpox Spread
The virus that causes chickenpox lives in the nose and throat and is sprayed into the air when an infected person sneezes, coughs or talks. It is also in the blisters and rash. Chickenpox is spread from person to person by coughing, sneezing, or touching the rash. People with chickenpox can spread the disease from 1 2 days before symptoms start and until all the blisters are crusted over . However, people with weak immune systems are contagious longer, usually as long as new blisters keep appearing. Symptoms usually appear about 10 21 days after exposure to the virus.
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Possible Risks Of Chickenpox Immunization
Possible mild effects are tenderness and redness where the shot was given, fever, tiredness, and a varicella-like illness. There is a very small chance of an allergic reaction with any vaccine.
A rash can happen up to 1 month after the injection. It may last for several days but will disappear on its own without treatment. There is a very small risk of after vaccination with MMRV.
Risk And Side Effects

Side effects of the vaccine may include:
- Soreness at the injection site
- Redness at the injection site
- Rash at the injection site
- Fever
Anyone who gets a rash after being vaccinated may be able to pass the virus to another person. In that case, they are advised to stay away from infants and people who have compromised immune systems.
It’s also possible that people may develop shingles , which causes a painful rash, years after getting the vaccine. However, shingles occurs less often after getting the chickenpox vaccine than after having a chickenpox infection.
Because the chickenpox vaccine contains a live, weakened virus, people who have compromised immune systems may develop a severe and potentially life-threatening infection after getting the vaccine. The vaccine is not recommended for people who have a compromised immune system.
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How It Is Transmitted
Varicella is solely a human disease and is one of the most readily infectious illnesses. The virus can be spread by direct contact with fluid in the lesions or through the airborne spread from the respiratory tract. The attack rate among susceptible contacts in household settings is estimated at 65%-87%.
How Do You Avoid Chickenpox
Immunization is the best way to protect yourself, your children and your community.
If you have chickenpox, stay home for at least 5 days after the rash starts or until all the blisters have scabbed. Wash and disinfect articles that may have been in contact with the rash or any fluid from the nose or throat. Remember to wash hands often.
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Other Reported Adverse Events And Conditions
Herpes zoster
HZ has been reported after varicella immunization. The risk of developing HZ is 4-fold to 12-fold lower in vaccinated as compared with unvaccinated children under 10 years of age who have had wild-type varicella. Severity of HZ has also shown to be reduced in vaccinated children compared to children with a history of wild-type VZV infection. The risk of HZ after vaccination with MMRV vaccine is unknown.
Transmission of vaccine virus
Transmission of vaccine strain virus from a healthy vaccine recipient is very rare. There have been few documented cases, all associated with a rash in the vaccine recipient.
Are There Side Effects Associated With The Chickenpox Vaccine
All medicines have potential side effects. But the side effects associated with the varicella vaccine are generally mild. The most common are pain, redness, or swelling at the injection site. A small percentage of people develop a mild rash, usually around the spot where the shot was given. Severe side effects are very rare.
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If We Immunize Children With The Varicella Vaccine Won’t They Be More Likely To Get Chickenpox As Adults
Chickenpox is much more likely to cause severe disease in adults than in children. Adults are 10 times more likely to be hospitalized when they have chickenpox than are children. Therefore, one thing that you would never want the vaccine to do is shift the disease from childhood to adulthood. However, for a number of reasons, this is unlikely to happen:
- Several studies have shown that immunity to chickenpox lasts at least 20 years and is probably life-long.
- The varicella vaccine is made in a manner similar to the rubella vaccine. We immunize little girls with the rubella vaccine to protect them from catching rubella when they become pregnant as adults an event that occurs 20, 30, or even 40 years later. And it works. The incidence of birth defects from rubella has decreased from as high as 20,000 cases per year to fewer than five cases per year.
- Measles vaccine, also made in a similar way, has been successfully used for more than 40 years without seeing a similar shift in age of disease.
Therefore, fading immunity, and a consequent shift of chickenpox infections from childhood to adulthood, is extremely unlikely to occur.
Drug Cost Containment Strategies In The Us
In the United States there are many resources available to patients to lower the costs of medication. These include copayments, coinsurance, and deductibles. The is another example.
Generic drug programs lower the amount of money patients have to pay when picking up their prescription at the pharmacy. As their name implies, they only cover generic drugs.
Co-pay assistance programs are programs that help patients lower the costs of specialty medications i.e., medications that are on restricted formularies, have limited distribution, and/or have no generic version available. These medications can include drugs for HIV, hepatitis C, and multiple sclerosis. Patient Assistance Program Center has a list of foundations that provide co-pay assistance programs. It is important to note that co-pay assistance programs are for under-insured patients. Patients without insurance are not eligible for this resource however, they may be eligible for patient assistance programs.
Patient assistance programs are funded by the manufacturer of the medication. Patients can often apply to these programs through the manufacturer’s website. This type of assistance program is one of the few options available to uninsured patients.
The out-of-pocket cost for patients enrolled in co-pay assistance or patient assistance programs is $0. It is a major resource to help lower costs of medications however, many providers and patients are not aware of these resources.
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Are There Side Effects From The Vaccine
Most reactions tend to be mild and include some soreness, redness, itching and/or a rash where the needle was given. A low-grade fever may occur.
Some children may get a very mild case of chicken pox one or two weeks after they get the vaccine but are not likely to be contagious.
Severe reactions are rare.
Please report any side effects or severe vaccine reaction to your doctor/nurse practitioner or local public health unit.
I Recently Had The Chickenpox Vaccine And Have Just Found Out I’m Pregnant What Should I Do

If you find out you’re pregnant within a month of having the chickenpox vaccine, it’s best to contact your GP for advice.
Do not worry. A study in the US of nearly 700 women who’d received the chickenpox vaccine while pregnant found no cases of babies affected by the vaccine.
Page last reviewed: 23 January 2019 Next review due: 23 January 2022
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Who Should Be Vaccinated Against Chickenpox
Chickenpox vaccination is recommended and funded in New Zealand for the following groups:
- children turning 15 months of age
- children turning 11 years of age who have never been infected with or previously vaccinated against chickenpox.
The vaccine is funded for certain high-risk individuals and/or their close contacts, regardless of age. People with a weakened immune system are at high risk, but may not be able to have the vaccination themselves, so it’s recommended that close contacts of these people be vaccinated. Discuss this with your GP.
Chickenpox vaccination is also recommended, but not funded, for:
- teenagers and adults who have never been infected with or vaccinated against chickenpox
- women who are planning a pregnancy and have never been infected with or vaccinated against chickenpox, such as those born and raised in tropical countries
- people who are not immune to chickenpox and who are working in professions where they come into contact with young children
- parents who have not had chickenpox.
When Should Adults Be Vaccinated Against Chickenpox
All adults who have never had chickenpox or received the vaccination should be vaccinated against it. Two doses of the vaccine should be given at least four weeks apart.
If you’ve never had chickenpox or been vaccinated and you are exposed to chickenpox, being vaccinated right away will greatly reduce your risk of getting sick. Studies have shown that vaccination within three days of exposure is 90% effective at preventing illness vaccination within five days of exposure is 70% effective. If you do get sick, the symptoms will be milder and shorter in duration.
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Who Should Not Be Vaccinated Against Chickenpox
Chickenpox vaccine is a live vaccine. This means that it can cause chickenpox, although it is usually milder, and it should not be used for certain groups of people who have reduced infection-fighting ability , such as if you:
- are pregnant
- are taking high-dose oral steroids such as prednisone or dexamethasone
- are getting chemotherapy or radiation
- have a condition that reduces your immunity such as cancer or HIV
- have active untreated TB
- have had another live vaccine within the past 4 weeks.