Bacterial Vaccines

BACTERIAL VACCINES

Typhoid Paratyphoid A, B (TAB vaccine)

It is a sterile suspension, 1 ml containing 1 × 109 S. typhi and 7.5 × 108 each of S. paratyphi A and B organisms in 5, 10 ml vials. Dose—0.5 ml s.c., 2–3 injections at 2–4 weeks intervals. Local tenderness, fever and malaise lasting 1–2 days are common after the first dose. It is estimated to be 70% effective in preventing enteric fever for 1 year. Booster doses may be given every 2–3 years.

Vi Typhoid Polysaccharide Vaccine

It contains purified Vi capsular antigen of S. typhi. A single 0.5 ml s.c./i.m. dose affords 72% protection at 18 months and 60% protection at 3 years. It produces much less local and systemic side effects than TAB and induces longer lasting immunity, but does not protect against paratyphoid A and B. Thus, it is an improvement over the whole cell TAB vaccine. However, it is not approved for use in children below 2 years and in pregnant women.

VACTYPH, TYPHIM Vi, TYPHIVAX 0.025 mg in 0.5 ml inj; repeat after 3 years.

‘Typhoid-Ty21a’ Oral Vaccine

This is a newer live oral typhoid vaccine prepared from Ty 21a attenuated strain of S. typhi which lacks the Vi polysaccharide and is nonpathogenic. The attenuation is due to absence of the enzyme Uridine diphosphate galactose4 epimerase which is essential for the production of lipopolysaccharide ‘O’ antigens. It is avirulent. By lodging in the intestinal mucosa it protects against S. typhi invasion of the gut in addition to imparting systemic immunity. High cell mediated and modest antibody mediated immunity is produced. Administered as 3 doses on alternate days in the form of enteric coated capsules it affords protection for 3 years. Efficacy is better than TAB. Trials in India and other countries have reported 67–90% protection at 3 years. Side effects are negligible: only 2% cases have reported diarrhoea, abdominal pain or rashes. It is much more convenient, safer and longer acting. It is not approved for use in children below 5 years and in pregnant women.

TYPHORAL S. typhi strain Ty21A 109 organism per cap; 3 caps taken in 3 doses on alternate days in between meals.

Cholera Vaccine

It is a suspension of phenol/formalin killed Inaba and Ogawa strains of V. cholerae, each ml containing 8 × 109 organisms in 5, 10, 30 ml vials. Dose: 0.5 ml s.c. or i.m. followed by 1 ml 1–4 weeks later, or a single dose of 1 ml for mass innoculation. Immunity, sufficient to prevent clinical disease, is produced only in 50% of those innoculated, and lasts 6 months or so—sufficient to tide over an epidemic. Cholera innoculation during congregations (melas) has not reduced the incidence of the disease (because it takes 2–3 weeks for immunity to develop): this practice has been discontinued. It also does not prevent carrier state. Transient local soreness, low grade fever, aches and pains lasting 1–2 days are common. Neurological complications are rare.

Two new oral cholera vaccines have been produced: killed whole cell/recombinant B subunit (WC/r BS) and live CVD103 HgR vaccine. Both these vaccines are highly immunogenic, safer than the present cholera vaccine and provide immunity upto 3 years. Cumulative protective efficacy of 86% at 3 weeks and 50% at 3 years have been estimated. They have been made available in Europe, but not yet in India.

Whooping Cough (Pertussis) Vaccine

It is killed 2 × 1010 organisms/ml suspension of B. pertussis organisms. Dose 0.25–0.5 ml s.c. or i.m. thrice at 4 week intervals in infants and children below 5 years (whooping cough is very rare after 5 years age).

It also induces a state of diminished β adrenergic reactivity and aids sensitization to other antigens.

In addition to local pain and induration, severe systemic (even fatal) reactions have been reported, but extremely rarely—high fever with hypotonic hyporesponsive child, convulsions, alterations of consciousness and focal neurological signs. Once any such reaction has occurred, further doses are contraindicated. It is also contraindicated in children with history of convulsions or other neurological disease.

It is a component of triple antigen: seldom used separately.

Meningococcal A&C Vaccine

It contains purified capsular polysaccharide of N. meningitidis group A and C, 50 μg of each per unit in single dose and 10 dose vials. One dose (0.5 ml s.c. or i.m.) is indicated for prophylaxis of meningitis during an epidemic caused by group A or C meningococci.

MENINGOCOCCAL A & C, MENCEVAX A & C 0.5 ml amp, 5 ml vial.

Haemophilus Influenzae Type b (Hib) Vaccine

It contains medium oligosaccharide of H. influenzae type b (10 μg) conjugated with  nontoxic protein (25 μg) of CRM₁₉₇ mutant C. diphtheriae  toxin  along  with  alum.  hydrox. adjuvant.  It is indicated for protection of infants and children against H. influenzae meningitis, pneumonia, etc. Infants 2–6 months are given 3 doses (0.5 ml i.m.) at 8 week gaps, 7–11 months 2 doses, while those older than 1 yr require only 1 dose. Good antibody response and protection has been obtained in > 90% recipients.

VAXEMHIB,  HIBTITER 0.5 ml and 5 ml vials

Antiplague Vaccine Formalized

It contains 2 × 10⁹ Y. pestis organisms per ml, killed by formaline, in 10 ml vial. Dose—1 ml i.m. twice 1–2 weeks apart or 2 ml single dose. Local and systemic reactions are relatively frequent and increase with the number of booster doses. Immunity lasts 6–8 months—sufficient to cover an epidemic. Plague is now rare, so is the need for this vaccine.

Bacillus Calmette-Guérin (BCG) Vaccine

It is a live vaccine bearing an attenuated bovine strain of M. tuberculosis, developed in 1921 by Calmette and Guérin in France. It is supplied as 0.5–1 mg dry powder (1–2.5 × 107 colony forming units) in ampules to be suspended in 1 ml of sterile water; 0.05 ml (in neonate) 0.1 ml (older individuals) is injected intracutaneously in the left deltoid region at birth. In children and adults tuberculine testing is done beforehand and BCG is given only to negative responders.

A red painless papule appears after 7–10 days; reaches about 8 mm diameter in 5 weeks with swelling of axillary lymph node; may ulcerate, but scales and dries in 3 months; totally heals in 6 months. The protection afforded by BCG is partial and neither permanent nor entirely predictable. It has been widely used to enhance resistance to tubercular infection, but doubt has been cast about its utility in adults, though children appear to be benefited.

BCG has also been used to enhance immunity nonspecifically by stimulating the reticuloendothelial system: employed as adjuvant in immunotherapy of cancer and some other conditions. It is contraindicated in tuberculine positive individuals, in those with compromised host defence including HIV positive children, and during pregnancy.