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Indian Pediatr 2017;54: 426 |
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Clippings
Theme:
Immunization
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Vipin M Vashishtha
Email:
[email protected]
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Intranasal and sublingual delivery of Inactivated
Polio Vaccine (Vaccine. 2017 Apr 8. pii: S0264-410X(17)30442-5.
doi: 10.1016/j.vaccine.2017.03.090. [Epub ahead of print])
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The current study evaluated the possibilities of polio vaccination via
mucosal surfaces using Inactivated polio vaccine (IPV) based on
attenuated Sabin strains. Mice received three immunizations with
trivalent sIPV via intramuscular injection, or via the intranasal or
sublingual route. The need of an adjuvant for the mucosal routes was
investigated as well, by testing sIPV in combination with the mucosal
adjuvant cholera toxin.
Both intranasal and sublingual sIPV immunization
induced systemic polio-specific serum IgG in mice that were functional
as measured by poliovirus neutralization. Intranasal administration of
sIPV plus adjuvant induced significant higher systemic poliovirus type 3
neutralizing antibody titers than sIPV delivered via the intramuscular
route. Moreover, mucosal sIPV delivery elicited polio-specific IgA
titers at different mucosal sites (IgA in saliva, fecal extracts and
intestinal tissue) and IgA-producing B-cells in the spleen, where
conventional intramuscular vaccination was unable to do so.
Comment: This study seems to be a polio
strategist’s delight wherein the best attributes of the two main polio
vaccines are utilized in a single product. Mucosal responses are
important because they prevent establishment of initial infection at the
port of entry and subsequent dissemination to other sites. If the
results are reproduced in human studies, the intranasal and sublingual
routes may prove to be valuable approaches for routine vaccination and
outbreak control in the post-eradication era.
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Tdap administered during pregnancy is
effective in protecting infants against pertussis (Pediatrics.
2017;139:e20164091).
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In this retrospective cohort study of infants born at Kaiser Permanente
Northern California from 2010 to 2015, the researchers estimated the
effectiveness of maternal pertussis vaccination for protecting newborns
against pertussis in the first 2 months of life and in the first year of
life accounting for each infant DTaP dose. Among 148,981 newborns, the
vaccine effectiveness of maternal tetanus toxoid, reduced diphtheria
toxoid, acellular pertussis (Tdap) vaccine was 91.4% (95% CI 19.5 to
99.1) during the first 2 months of life and 69.0% (95% CI 43.6 to 82.9)
during the entire first year of life. The vaccine effectiveness was
87.9% (95% CI 41.4 to 97.5) before infants had any DTaP vaccine doses,
81.4% (95% CI 42.5 to 94.0) between doses 1 and 2, 6.4% (95% CI "165.1
to 66.9) between doses 2 and 3, and 65.9% (95% CI 4.5 to 87.8) after
infants had 3 DTaP doses.
Comment: Maternal vaccination with Tdap
currently seems to be the most effective strategy to protect young
infants against pertussis. All other strategies including ‘cocoon
vaccination’ with Tdap have not been effective, as it relies on herd
immunity, which is not sufficiently well induced by acellular pertussis
(aP)-containing products. In fact, this is the only valid and effective
indication of use of available Tdap vaccine now, considering
unexpectedly faster waning of aP vaccine induced immunity. However,
there are certain issues like optimum timing of the maternal Tdap
vaccination, possible interference with first infant dose of pertussis-containing
vaccine, and hyper-immunization with tetanus and diphtheria toxoid;
these need to be sorted out.
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Interchangebility of pneumococcal conjugate
vaccines (PCVs) — Divergent memory B-Cell responses in a mixed
infant PCV schedule (Pediatr Infect Dis J. 2017;36:e130–5)
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Vaccine-induced immunity against pneumococcal infection relies on the
generation of high concentrations of antibody and B cell memory. Both
the 10- and the 13-valent pneumococcal conjugate vaccines (PCV-10 and
PCV-13) effectively reduce disease caused by vaccine serotypes. It is
unknown whether the generation of B cell memory requires several doses
of the same vaccine or whether different PCVs are interchangeable.
Children in the United Kingdom (n=178) who had
previously received PCV-13 at 2 and 4 months were randomized 1:1 to
receive a PCV-13 or PCV-10 booster at age 12 months. Peripheral blood
memory B cells (BMEM) were quantified before and at 1 and 12 months
after vaccination using a cultured enzyme-linked immunospot assay for
pneumococcal serotypes 1, 3, 4, 9V, 14, 19A, and diphtheria and tetanus
toxoid. Correlations between BMEM frequencies and simultaneously
measured antibody (IgG and opsonophagocytic assay) was also assessed.
A significant rise in post-booster BMEM frequency was
seen for 5 out of 6 serotypes in the PCV-13 group and none in the PCV-10
group. In the PCV-13 group, there was a particularly large increase in
serotype 3–specific BMEM associated with only a small increase in
antibody. Post-booster BMEM responses correlated positively with
antibody, but correlations between pre-booster BMEM and subsequent BMEM
and antibody responses were inconsistent.
Comments: The scarcity of the vaccines –
such as recently witnessed with IPV – would bring the issue of
interchangebility of PCVs in the limelight. The above study suggests
that immunizing with a PCV-containing polysaccharides conjugated to a
novel carrier protein is not sufficient to generate a rapid and strong
B-cell memory response, at least when primary vaccination with PCV-13 is
followed by a booster dose of PCV-10.
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