There are several strains of meningococcus. The most common are called Groups A, B, C, Y and W. Vaccines are used routinely to protect against groups ACYW. A new vaccine against group B was approved for use in Canada in 2013.
In Canada since 2007, Group B strains have caused almost 60% of cases or an average of 111 cases per year. The frequency of group B cases does not vary very much from year to year. However, the number of cases caused by group C, Y and W do vary of time. The frequency of Group C disease has decreased significantly since the introduction of routine immunization with Group C conjugate vaccine in 2005-6 in infants and older children. From a peak of 202 cases in 2001, the number of group C cases decreased by 90%, to an average of 19 cases between 2007-2011. The average annual number of cases caused by serogroup W and Y since 2007 were 11 and 34 respectively.
Group A strains causes large epidemics somewhere in Africa almost every year and epidemics have also occurred in India, Pakistan, Nepal, and China in recent years. There have been no group A epidemics in Canada or USA for over 65 years.
Local outbreaks of meningococcal disease in which 2 or more cases occur in a school or college have been occurring in Canada and other countries for the since 1989. Although most of these outbreaks were caused by Group C strains prior to 2005, such outbreaks have become rare in USA and Canada because of the use of vaccines.
As with pneumococcal and Hib vaccines, the meningococcal vaccines most commonly used in Canada today are the conjugated polysaccharide vaccines.
Three meningococcal group C Conjugate Vaccines composed of the purified polysaccharide linked to a protein have been approved for use in Canada. The brand names of the conjugate vaccines are:
The polysaccharide vaccines do not stimulate adequate immune responses in infants. As a result, the vaccine does not protect children under two years of age from Group C disease. The duration of protection after immunization with the polysaccharide vaccines is thought to be 3 to 5 years in adults and less in children.
The group C conjugate vaccines are very safe and stimulate production high levels of protective antibodies in infants and young children. Studies in Canada of infants immunized with the conjugate vaccines at 2, 4, and 6 months of age showed that local tenderness, redness, and swelling occurred less frequently after the group C conjugate vaccine than after the combined diphtheria-tetanus-acellular pertussis-polio-Hib vaccine. Rates of fever, irritability, crying, and other systemic reactions were not increased by the addition of the group C conjugate vaccine. Over 15 million infants and children have received the conjugate C vaccine: no serious reactions have been observed.
The meningococcal C conjugate vaccine protects only against disease caused by group C strains. It does not protect against disease caused by other groups of meningococci. Starting November 1999, a large scale immunization program was undertaken in England and Wales to immunize all children less than 18 years of age with the group C conjugate vaccine and to use the vaccine for routine immunization of all infants starting at 2 months of age. Use of the vaccine has been very successful in controlling all forms of disease caused by group C meningococcus. Similar programs have been started in other European countries. The meningococcal C conjugate vaccine is now available at no cost to parents throughout Canada.
In Alberta, the C conjugate vaccine is administered at 2, 4, and 12 months of age; in British Columbia at 2 and 12 months of age; and in the rest of Canada, a single dose is given at 1 year of age. In addition, most provinces recommend routine vaccination of children at 10-14 years of age with one dose of either the group C conjugate vaccine or the ACYRconjugate vaccine.
Follow-up studies in England have shown that a single dose of the C conjugate vaccine protects against group C disease for 4-5 years in children 2 years and older. However, the duration of protection seems to wane much more rapidly in infants vaccinated between 2 and 23 months of age. It is recommended that a booster dose be given to children vaccinated before their second birthday in order to provide more lasting protection. An additional booster at 10-14 years of age may also be necessary.
Three combined Groups ACYW Conjugate Vaccines have been approved for use in Canada in children 2 years of age and older, adolescents and adults. The polysaccharides have been linked to a protein (diphtheria toxoid, Menactra®; CRM protein, Menveo®, or tetanus toxoid, Nimenrix). These vaccines provides much broader protection than group C conjugated vaccine. Increase in the frequency of disease caused by groups Y and W have been observed in Canada, USA, England, and other parts of the world. Therefore, the broader coverage provided by the combined ACYW conjugate vaccine makes it preferable to the C conjugate vaccine.
The combined ACYW conjugate vaccines are very safe. Local reactions in children and adolescents are similar to those seen with diphtheria-tetanus toxoid. Fever and other systemic reactions are mild and brief in duration. There is no scientific evidence that vaccination with ACYW conjugate vaccine increases the risk of Guillain Barré Syndrome, a rare form of paralytic disease.
The vaccines produce very high antibody concentrations against all four polysaccharides. Protective levels of antibodies persist for at least 4 years. This vaccine has replaced the group C conjugated vaccine in school-based programs aimed at immunizing pre-teens in Alberta, New Brunswick, Newfoundland and Labrador, Ontario, PEI, and Saskatchewan as well as for new recruits joining the Canadian Forces. Other provinces and territories continue to use the C conjugate vaccine in both infants and pre-teens.
Recent studies have demonstrated the both combined ACYW conjugated vaccines are safe and effective in stimulating immunity in infants. However, a several injections are required in the infant series, as with other infant vaccines.
A new vaccine [Bexsero®] against serogroup B meningococci was approved for use in Canada in 2013. It has also been approved for use in the European Union, England, Ireland, and Australia. The vaccine has been studied in infants, children, and adolescents and is approved for use from 2 months to 17 years of age.
Unlike groups A, C, W, and Y, the group B polysaccharide cannot be used as a vaccine because it does induce the immune system to make protective antibodies. The new B vaccine consists of 3 purified proteins derived from the outer surface of group B meningococci combined with the outer membrane vaccine used in New Zealand during the outbreak of group B disease. The use of multiple components in the vaccine is necessary in order to provide protection against the many different group B strains.
The B vaccine has been shown to be effective in inducing antibodies which kill at least 80% of group B strains. Such antibodies are protective against disease.
The B vaccine is also safe. No serious adverse events have been reported after its use. Local reactions at the site of the injection occur in about 20% of children. The redness, swelling, and pain are usually mild and last only a day or so. Severe reactions are very rare. Fever, irritability, crying, loss of appetite, or other general reactions are uncommon with all of the polysaccharide vaccines. However the new vaccine against group B meningococcus is associated with an increased rate of fever in infants at 2, 4, and 6 months of age when it is given at the same visit as the routine infant vaccines. The fever is usually between 39-40°C and rarely lasts more than 48 hours. Fever can be controlled with acetaminophen if necessary.