The ideal vaccine
“An ideal vaccine should confer long-lasting, preferably lifelong protection against the disease with a single or a small number of doses. It should be inexpensive enough for wide-scale use, stable enough to remain potent during shipping and storage, and should have no adverse effect on the recipient.” (Canadian Immunization Guide)
While some vaccines come close to these criteria, others do not. Each vaccine has its own benefits and risks, indications and contraindications. Generalizations are difficult to make. This is intended as a guide for the medical student/pediatric resident when confronted by a parent who does not want their child vaccinated. It is intended to address common fears, dispel myths and expose truths of vaccines.
Take note that only infections that are restricted to humans and do not involve other hosts, such as smallpox, poliomyelitis, and measles, can be eradicated. Smallpox is already eradicated, and the immunization program against smallpox was therefore discontinued, a success story to the effectiveness of vaccinations.
Types of vaccines
Different types of vaccines are available, dependent upon the organism and the immunogenicity and route of administration. Recombinant vaccines are becoming more common (eg. Guardasil – HPV). There are also protein vaccines (Menactra – Meningococcus C) and polysaccharide vaccines (Quadrivalent Meningococcus vaccine). Polysaccharide vaccines are less immunogenic and can only be used in children 2 years of age or older. Many vaccines consist of inactivated organisms or purified components. Others, particularly vaccines against viral diseases, contain live microorganisms. Live vaccines have particular advantages including a small dose (the virus replicates in the recipient) and a stimulus that more closely resembles that associated with a natural infection. However, live vaccines present some challenges. They are difficult to store and may potentially be inactivated. It is often difficult to know who is eligible for a live vaccine; immunocompromised patients and pregnant women may be at risk. There is also the theoretical risk of viral shedding to immunocompromized contacts of live vaccine recipients. Although very rare, a live vaccine can produce some of the symptoms of the disease they are meant to prevent, though at a much lower intensity.
The importance of vaccination
Reasons to vaccinate
1. Vaccines prevent uncommon diseases.
As mentioned above, smallpox has been eradicated thanks to a worldwide vaccination program. Similarly, Polio has been eradicated in the Western countries. Several other vaccinated conditions have become very uncommon since vaccinations were started. For example, there were 12,000 cases and 1,000 deaths per year due to Diphtheria prior to the vaccination program was initiated, whereas there is now only 5 cases and no deaths per year in Canada. See table 1 for a summary of diease prevalence in Canada before and after vaccines were implemented.
Average number of cases and related deaths per year
|Diphtheria||12,000 cases and 1,000 deaths||5 cases and 0 deaths|
|Tetanus||60 cases and 40 deaths||2 cases and 0 deaths|
|Pertussis||30,000 cases and 50 deaths||3000 cases with 5 deaths|
|Polio||2,000 cases in last epidemic in 1969||0|
|Haemophilus Influenza||1500 cases of meningitis||Less than 50 cases, 0 deaths|
|Measles||300,000 cases with 300 deaths and 300 cases of brain damage||Less than 50 cases with 0 deaths|
|Mumps||30,000 cases||95 cases|
|Rubella||85% of children had rubella by age 20. 200 cases of congenital rubella||3 babies with congenital rubella syndrome born to unvaccinated mothers|
2) Vaccines prevent serious diseases with devastating consequences
Parents often are often under the impression that vaccine preventable conditions are benign, that they are more a nuisance than a serious disease with serious complications. Understandably they would rather have their child have the naturally acquired disease than the vaccine (in fear of the complications of vaccines). Contributing to this misconception is the rarity of these conditions in our era of vaccinations where the disease and its consequences are seen so seldom. Pointing out the severe nature of the vaccine preventable illnesses and associated complications can help place things in perspective.
Table 2 directly compares the Disease outcomes to the risk of the particular vaccine.
|Disease||Disease Outcomes||SE/Risk of vaccine|
|Diphteria||Sore throat, weakness, nerve damage, heart failureDeath in 10%||DTaPLocal redness.5% may have fever|
|Tetanus||Muscle spasms, Seizures.Death in 50%|
|Pertussis||Wooping cough.Death 1 in 400 infants.|
|Polio||Muscle paralysis in 1%||IPV – local reaction|
|Hib||Meningitis – 5% mortality. OME – deafness in 15%||Hib – local reaction|
|Measles||Bronchitis, fever, rash, encephalitis in 0.1%||MMR – 1 in 24,000 get low plt.25% of adult women develop joint pain to rubella vaccineRubella vaccine is live attenuated virus – do not use in immunocompromise/ pregnancy|
|Mumps||Encephalitis in 0.5%|
|Rubella||Congenital Rubella Syndrome or Stillborn|
3) Vaccination contributes to herd immunity
In order to obtain the benefit of vaccinations, the majority (more than 95%) of any given population need to be vaccinated. As long as there is an unvaccinated population, the risk of transmission remains higher and outbreaks cannot be prevented.
4) Experts recommend vaccinations
Immunizations are recommended by the major governing bodies including the Canadian Paediatric Society (CPS), the American Academy of Pediatrics (AAP) and Health Canada’s National Advisory Committee on Immunization (NACI).
The World Bank has stated that immunization should be first among the public health initiatives in which governments around the world invest. Vaccination programs are considered to be the most cost-beneficial health interventions and one of the few that systematically demonstrate far more benefits than costs. (see cost per life year saved Table in CIG)
Myths about vaccines
1) Vaccines are not safe
- As outlined in Table 2, vaccines are generally safe. The most common reaction is a local reaction at the site of injection involving tenderness, bleeding, hematoma or local infection. Systemic reactions may include fever, rash, joint and muscle pain, fainting or seizures however the latter is very uncommon. Anaphylaxis to the vaccine or a component therein is seen in 1 to 3 out of a million cases.
2) Too many vaccines at once overwhelms the child’s immune system
- There is no evidence to support this claim. The human immune system has redundancy built in, to the point that the immune response to a vaccine given in isolation is similar to that same vaccine given in combination with other vaccines.
3) Vaccines weaken the child’s innate immune system
- Exposure to components in the vaccine rather activates the child’s immune system to better target against disease causing pathogens. This does not weaken the immune system, but helps the immune system to build immunity.
4) MMR causes inflammatory bowel disease
- There is no conclusive evidence to support this
5) MMR causes Autism
- There is no causal association found. This debate began in 1998 when an article was published in the Lancet by Dr. Wakefield and 12 co-authors who claimed to have found a link between the MMR vaccine and autism in a small study of 12 children. The co-authors withdrew their names from the study and it was retracted, when it was found that Dr. Wakefield had a fatal conflict of interest. He was doing paid research for a group of parents of autistic children who were trying to mount a suit against the makers of the MMR vaccine. Dr. Wakefield was sentenced for this publication as the data was skewed and in-accurate. Since then, numerous large peer-reviewed studies have been published that found no link.
6) Vaccines are not necessary-the diseases are gone.
- From the above incidence data it is clear that although fewer cases are found, only small pox have been completely eradicated. To prevent outbreaks, authorities say that at least 95% of the population need to be vaccinated (See: Herd immunity above)
7) Vaccines contain poisonous substances
- This debate has its origins in the debate about the MMR vaccine causing Autism. It was thought that Thimerosal (a preservative used in multi-dose vials) might be the agent explaining the association demonstrated by Dr. Wakefield. Since then Thimerosal have been removed from all vaccines in Canada due to the concern of a higher than acceptable Mercury content found in Thimerosal.
8) Natural medicines provide safer protection
- No evidence
What vaccines should children receive? (link to bc schedule)
The Canadian Paediatric Society (CPS), the American Academy of Pediatrics (AAP) and Health Canada’s National Advisory Committee on Immunization (NACI) recommend the following vaccines:
- 6-in-1 (including DTaP-Hib, polio, and Hepatitis B)
- These vaccines protect against diphtheria, tetanus, (acellular) pertussis (whooping cough), polio, and Haemophilus influenzae type B (Hib).
- This vaccine protect against measles, mumps, and rubella.
- Varivax (Varicella/Chickenpox)
- Pneumococcus (13 – valent is standard, 23 – valent available for high risk groups)
- This vaccine protects against infections caused by Streptococcus Pneumonia including meningitis and pneumonia as well as other sino-pulmonary infections.
- Meningococcus (Men-C is standard, quadrivalent available for high risk groups)
- This vaccine protects against sepsis and meningitis caused by Neisseria Meningitidis
- HPV (Human Papilloma Virus)
- For prevention of cervical cancer and genital warts
- Covers strains 6, 11, 16, 18
- Oral vaccine
- Annual Influenza virus vaccine
- Recommended for all children older than 6 months of age, especially those at high risk of complications from influenza, such as those with heart problems, chronic lung diseases and other chronic diseases such as diabetes.
Questions to Ask:
Taking a history relevant to vaccines:
- Historical Investigations:
- Present health (pregnant, immunocompromised)
- Current medications
- Allergies (eggs, previous anaphylaxis to vaccines)
- Vaccination History:
- Which vaccinations
- When administered
- Where administered
- How many doses
Contraindications (see Table-precautions/CI for specific vaccines in CIG)
Colds: Minor illnesses such as the common cold, with or without fever, frequently occur in young children and are not contraindications to immunization. Such infections do not increase the risk of adverse effects from immunization and do not interfere with immune responses to vaccines. Deferring immunization because of acute mild illnesses often results in incomplete immunization.
Moderate to severe illness with or without fever: is reason to defer routine immunization with most vaccines. This precaution avoids superimposing adverse effects from the vaccine on the underlying illness or mistakingly identifying a manifestation of the underlying illness as a complication of vaccine use. However, if the vaccine is required because of likely exposure to disease or if timely immunization is unlikely, the vaccine may be given despite the intercurrent illness.
Allergic conditions (eczema, asthma): are not contraindications to immunization unless there is a specific allergy to a vaccine component. Individuals that are allergic to eggs should take special precautions.* (see below)
Egg allergy: no special precautions are necessary for children with minor egg hypersensitivity if they can uneventfully ingest quantities of egg as a food ingredient. No special measures are necessary for children who have never been fed egg before their MMR immunization. In children that have had a severe allergy to egg, the Influenza vaccine is offered in a divided dose, in a controlled hospital setting where anaphylaxis may be rapidly responded to should it occur. Under close observation, 10% of the dose is first given, and followed with the remainder of the dose if the initial dose was tolerated by the patient. No special precaution needs to be taken with the MMR vaccine.
Pregnancy: Immunization of pregnant women with a killed or recombinant vaccine is safe. However, the use of live, attenuated vaccines is contraindicated in pregnancy. Infections that may cause congenital abnormalities in the embryo or fetus, such as rubella or varicella, are best prevented by vaccinating either children or the woman before pregnancy. Although there is some evidence that inadvertent administration of live virus vaccines (e.g. measles, mumps, rubella, and varicella) during pregnancy does not provoke problems either in the fetus or in the developing infant, current guidelines state that reasonable precautions should be taken to prevent administration of these vaccines during the 3 months before pregnancy and thoughout, to prevent the theoretical risk of infecting the fetus. Inadvertent vaccination of a pregnant woman with live virus vaccines should not be considered a reason to recommend termination of the pregnancy. No malformation, learning disability, hearing impairment or malignancy developed in any of the children whose mothers were inadvertently vaccinated with live vaccines (poliomyelitis, influenza, diphtheria, and tetanus) while pregnant. In the instance when the risk of disease exposure is high and when the infection would pose a significant risk to an unvaccinated pregnant woman and her fetus, it may be necessary to consider vaccinating the woman during pregnancy. When a vaccine is indicated during pregnancy, consider delaying administration until the second or third trimester, if possible, to reduce the risk of inappropriate attribution of cause. The physician would be advised to contact an infectious disease specialist in this case, prior to administration of the vaccine.
Breastfeeding: breastfeeding does not adversely affect immunization of the infant with either live or killed vaccines and may, in fact, improve the immune response to some vaccines. Lactating mothers who have not received the recommended immunizations may be safely vaccinated against rubella, measles, mumps, tetanus, diphtheria, influenza, Steptococcus pneumoniae, hepatitis A, hepatitis B, polio and varicella.
Talking to patients and caregivers about immunization
Caregivers of children often have many questions regarding vaccine safety. It is important to understand the current issues facing parents today in order to effectively counsel parents regarding the safety and effectiveness of immunizations.
The success of vaccines in preventing diseases means that many parents, doctors or students have never seen a life-threatening case of diphtheria, polio or measles. Today, it is the misconceptions about vaccine safety that threatens vaccine programs. The health care provider’s role in educating caregivers appropriately is more important than ever.
Although signed consent is not required, parents and patients must always be informed about both the benefits and risks of vaccines. They should be reminded of the risks of the targeted diseases and given the opportunity to ask questions. It should also be recorded in the patient’s chart that the discussion took place.
- Pre-vaccination screening:
- Allergy to any component of the product(s)
- The best sites for subcutaneous or intramuscular immunizations are the deltoid area or the anterolateral surface of the thigh. The thigh is preferred in children <1 year because it is the largest muscle, while the deltoid is the preferred site for children >1 year to avoid complaints of limping due to muscle pain. The buttock is not recommended for routine immunizations.
- The injection site should be cleansed with an antiseptic (isopropyl alcohol) which is allowed to dry on the skin before the injection is given.
- Children should be restrained with help from their caregiver before injection.
- A separate, sterile needle and syringe should be used for each injection. For subcutaneous injections, a 25 gauge, 5/8 inch needle is recommended. It should be inserted at a 45 degree angle into the tissues below the dermal layer of skin. For intramuscular injections a longer needle (7/8 inch for infants, 1 inch for others) is required.
- Prior to injecting the vaccine, pull back on the plunger to ensure that you will not inject a blood vessel.
- Each person who is immunized should have a permanent personal immunization record.
- The health care provider must also maintain a separate, permanent record of the immunization history with headings as follows:
- Trade name of product
- Lot number (in case of recall)
- Disease(s) against which it protects
- Date given
- Site and route of administration
- Storage procedures:
- Refer to individual vaccines for specific instructions related to storage and handling including: multi-dose vials, lyophilized vaccines, light exposure, freezing, refrigeration, and expiry.
- Observing the patient post-vaccination
- Most symptoms of anaphylaxis begin within 30 minutes after an injection of vaccine. Shorter intervals to onset of symptoms usually foretell more severe episodes. Thus, it is prudent to keep vaccinees under observation for immediate reactions or syncope for a period of at least 15 minutes after inoculation if hypersensitivity is a possibility.
- Epinephrine should be available for immediate administration when immunizing agents are injected in order to treat the extremely rare by serious complication of anaphylaxis. (CIG)
Anaphylaxis Risk, Diagnosis and Management
1) Anaphylaxis risk
- Vaccines that contain small quantities of egg protein can cause hypersensitivity reactions in some people with allergies to eggs. The likelihood of such reactions occurring varies considerably among vaccines.
- Adverse reactions are more likely to occur to vaccines against yellow fever and influenza, which are prepared from viruses grown in embryonated eggs.
- Measles and mumps vaccine are grown in chick embryo cell culture and after several purification steps may contain trace quantities of avian proteins.
- Anaphylaxis after measles vaccination is rare. Nonetheless, it has been reported in people with anaphylactic hypersensitivity to eggs and in those with no history of egg allergy. In some of these instances, it may be hypersensitivity to gelatin that is responsible for the anaphylaxis.
2) Anaphylaxis Diagnosis
- The cardinal features of anaphylaxis:
- Itchy, urticarial rash (>90% of cases)
- Progressive, painless swelling (angioedema) about the face and mouth, which may be preceded by itchiness, tearing, nasal congestion or facial flushing.
- Respiratory symptoms, including sneezing, coughing, wheezing, laboured breathing and upper airway swelling (hoarseness, difficulty swallowing) possibly causing airway obstruction
- Hypotension, which generally develops later and can progress to shock and collapse.
- In true anaphylaxis, these changes develop over minutes and usually involve at least two body systems. Unconsciousness is rarely the sole manifestation of anaphylaxis. Thus, it is important to distinguish breath-holding spells and syncope that occur in some young children and infants when they are upset and crying hard.
3) Anaphylaxis Management
- Perform Step 1-4 rapidly or simultaneously:
- Call for assistance, including an ambulance
- Place the patient in the recumbent position, elevate feet if possible
- Establish oral airway if necessary
- Promptly administer 0.01 ml/kg (max 0.5 mL) of aqueous epinephrine 1:1,000 by subcutaneous or intramuscular injection in the opposite limb to that in which the vaccine was given. Subcutaneous injection is preferred for mild cases, while intramuscular injection is advised for severe reactions. Dosing can be repeated twice at 20 minute intervals (or 10-15 minutes for severe reactions) in a different limb with each administration.
- As an adjunct to epinephrine, a dose of 50mg/mL diphenhydramine hydrochloride (Benadryl) can be given. This should not delay the administration of Epinephrine. Oral treatment is preferred in the conscious patient.
- Monitor vital signs and reassess patient status frequently
- The patient should be transferred to an emergency department for a period of observation as 20% of anaphylaxis episodes follow a biphasic course with recurrence of the reaction after a 2-9 hour asymptomatic period.
Reporting Adverse Events
- Physicians and other health personnel should report serious adverse events associated with immunization to their local health unit or medical officer of health.
- A reporting form is available in the Compendium of Pharmaceuticals and Specialties (CPS)
- Updated reports on adverse events are published periodically and are available on the Health Canada website http://www.hc-sc.gc.ca/hpb/lcdc/bid/di/nation_e.html
- To enhance surveillance of rare but severe adverse events, Health Canada has implemented a pediatric hospital-based network: the Immunization Monitoring Program Active (IMPACT)
- Special review of serious and unusual events is conducted by the Advisory committee on Causality Assessment (ACCA) to determine the degree to which such events are linked to the implicated vaccine: http://www.nc-sc.gc.ca/hpb/lcdc/bid/di/acca_e.html
Canadian Immunization Guide – http://www.phac-aspc.gc.ca/publicat/cig-gci/
CPS Statement: Use of Influenza vaccines in children with an egg allergy. http://www.cps.ca/en/documents/position/influenza-vaccines-in-children-with-egg-allergy
CPS Statement: Preventing varicella: Recommendations for routine two-dose varicella immunization in children. http://www.cps.ca/en/documents/position/preventing-varicella
CPS Statement: Emergency treatment of anaphylaxis in infants and children. http://www.cps.ca/en/documents/position/emergency-treatment-anaphylaxis
HealthLinkBC – BC immunization schedule. http://www.healthlinkbc.ca/healthyliving/diseaseinjuryprevention/immunizationschedule.html
Written by: Erin Kennah (UBC MSI3)
Edited by: Elmine Statham (UBC Pediatrics Resident)