H e m a t o lo g y E d u c a t io n - European Hematology Association
H e m a t o lo g y E d u c a t io n - European Hematology Association
H e m a t o lo g y E d u c a t io n - European Hematology Association
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include the childhood infect<strong>io</strong>us illnesses (measles,<br />
mumps, rubella, diphtheria) pol<strong>io</strong>, pertussis, tetanus, hepatitis<br />
A and B, and influenza. Immunity to these agents is<br />
conferred by life<strong>lo</strong>ng product<strong>io</strong>n of protective antibodies.<br />
Immunity to some agents like tetanus is not permanent<br />
and may require vaccine boosts. The rat<strong>io</strong>nale for vaccinating<br />
SCT recipients is the observat<strong>io</strong>n that in the<br />
decade after transplant, antibody levels to many of these<br />
agents decline without further boosting. Internat<strong>io</strong>nally<br />
agreed guidelines drawn up by <strong>European</strong> and American<br />
stem cell transplantat<strong>io</strong>n groups, the Infect<strong>io</strong>us Disease<br />
Society of America and the Center for Disease Control<br />
recommend revaccinat<strong>io</strong>n of all SCT recipients within 2<br />
years of transplant with a full reimmunizat<strong>io</strong>n schedule,<br />
as well as yearly influenza vaccine. 7 While this is a very<br />
reasonable strategy, it is of interest to note that the risk of<br />
deve<strong>lo</strong>ping new infect<strong>io</strong>ns from childhood exanthems<br />
appears to be extremely rare in post SCT recipients even<br />
when not vaccinated. 3 However, it is anticipated that as<br />
more transplants using immuno<strong>lo</strong>gically naïve umbilical<br />
cord b<strong>lo</strong>od are performed, the risk of new infect<strong>io</strong>n from<br />
some of these agents will increase.<br />
Influenza virus<br />
SCT recipients remain at particular risk from severe<br />
and overwhelming infect<strong>io</strong>n with influenza virus for<br />
many months after SCT. The variability in influenza<br />
strains requires yearly administrat<strong>io</strong>n of vaccine for the<br />
prevalent strain and it is therefore appropriate to vaccinate<br />
all SCT recipients yearly (avoiding intranasal live<br />
virus vaccines) to prevent seasonal flu. 8 Patients undergoing<br />
all forms of SCT (auto<strong>lo</strong>gous and al<strong>lo</strong>geneic) are<br />
at risk from influenza and may not mount funct<strong>io</strong>nal<br />
protective immunity when vaccinated after transplant. 9<br />
The recent outbreak of new pandemic strain A/H1N1<br />
stressed the importance of having strategies in place for<br />
management of these patients. When the new pandemic<br />
H1N1 strain spread rapidly around the world, new<br />
vaccines were rapidly deve<strong>lo</strong>ped. Very little was known<br />
about the safety, immunogenicity, and optimal dosing<br />
regimen of 2009 H1N1 vaccine in the immunocompromised<br />
host, although several investigators reported efficacy<br />
of single dosing in healthy adults and children. 10–13<br />
A number of studies, including work by our group,<br />
demonstrated that vaccinat<strong>io</strong>n against 2009 pandemic<br />
H1N1 is associated with an acceptable safety profile in<br />
SCT recipients. 14–16 We found that the immune response<br />
in al<strong>lo</strong>geneic SCT recipients can be substantially<br />
improved by a second dose of vaccine, supporting the<br />
<strong>European</strong> Medicines Agency and the UK DoH guidelines<br />
for the administrat<strong>io</strong>n of two vaccine doses in this<br />
group of patients. 14 These data may also apply to vaccinat<strong>io</strong>n<br />
against other viral agents in the immunocompromised<br />
host and warrant further studies.<br />
Hepatitis B<br />
Whether transmitted from donor to recipient, reactivating<br />
in the recipient, or occurring de-novo, represents<br />
an important post-transplant problem because of the<br />
propensity of Hep B to cause liver damage. Patients who<br />
are Hep B surface and core antigen positive require<br />
lamivudine antiviral treatment post SCT. Negative<br />
seroconvers<strong>io</strong>n – the <strong>lo</strong>ss of protective antibody to Hep<br />
B – is an indicat<strong>io</strong>n to revaccinate. 17,18<br />
London, United Kingdom, June 9-12, 2011<br />
Tetanus<br />
Antibodies to tetanus fall after SCT. Revaccinat<strong>io</strong>n 1year<br />
post SCT is partially effective but immunity may<br />
decline within a year. 19<br />
Immunity to capsulated bacteria 20,21<br />
Since immunity to capsulated bacteria pneumococcus,<br />
haemophilus influenzae type B (HIB) and to a lesser extent,<br />
meningococcus depends on circulating antibodies, SCT<br />
recipients with defective antibody product<strong>io</strong>n are particularly<br />
at risk from these infect<strong>io</strong>ns. Notably patients<br />
who have been splenectomized and those with chronic<br />
GVHD are especially vulnerable. The problem with<br />
pneumococcal vaccines has been the incomplete coverage<br />
of all the common antigenic strains of the bacteria.<br />
However, the replacement of the earlier 7-valent vaccine<br />
(PCV7; Prevnar) by a 13-valent vaccine (Prevnar13),<br />
(both Pfizer Inc) is likely to provide more effective protect<strong>io</strong>n<br />
against pneumococcus in the SCT recipients.<br />
Despite the lack of data, the 13-valent vaccine is recommended<br />
for use in SCT patients until addit<strong>io</strong>nal studies<br />
have been performed. A clinical trial to assess the efficacy<br />
of this 13-valent vaccine in al<strong>lo</strong>geneic SCT recipients<br />
is ongoing.<br />
Immunity to DNA viruses after SCT<br />
The DNA viruses CMV, HSV, VZV, EBV, Adenovirus<br />
(ADV) BKV, and human papil<strong>lo</strong>mavirus (HPV), represent<br />
a group of viruses that can reside in the recipient<br />
life<strong>lo</strong>ng after primary infect<strong>io</strong>n. These viruses generate<br />
protective immunity in the immune competent host but<br />
can reactivate if immune funct<strong>io</strong>n falls off, as occurs<br />
after SCT. The reactivat<strong>io</strong>n of these viruses in an<br />
immune compromised host is potentially life-threatening.<br />
Unlike the prev<strong>io</strong>us categories of infect<strong>io</strong>us agents,<br />
immunity is largely cell mediated, and commercial vaccines<br />
have not been deve<strong>lo</strong>ped against these viruses.<br />
Fortunately, the antiviral agents, acyc<strong>lo</strong>vir, gancic<strong>lo</strong>vir,<br />
foscarnet, and cidofovir have activity against HSV, VZV,<br />
and CMV. Cidofovir has some efficacy against the BK<br />
virus and adenovirus. Furthermore, effective adoptive<br />
transfer of viral specific T cells can effectively control<br />
adenovirus, EBV, and CMV and rituximab can control<br />
EBV-related lymphoproliferative disease. 22–24 Two except<strong>io</strong>ns<br />
in this category are VZV and HPV, where effective<br />
vaccines exist and are being evaluated in SCT recipients.<br />
VZV<br />
Reactivat<strong>io</strong>n of VZV in the form of herpes zoster is a<br />
very frequent problem after SCT and while it can be suppressed<br />
with continuous treatment with acyc<strong>lo</strong>vir or<br />
valacyc<strong>lo</strong>vir, the virus typically reactivates promptly after<br />
discontinuat<strong>io</strong>n of antivirals. 25 A VZV vaccine represents<br />
a cheaper and more durable alternative to preventing<br />
zoster. However, vaccinat<strong>io</strong>n of recipients with repeated<br />
doses of live, attenuated VZV vaccine is only partially<br />
protective. 26 An alternative approach is to vaccinate the<br />
donor. Limited studies suggest this approach may be at<br />
least partially protective in the recipient. 27 Two new inactivated<br />
varicella vaccines are under deve<strong>lo</strong>pment.<br />
Hemato<strong>lo</strong>gy Educat<strong>io</strong>n: the educat<strong>io</strong>n programme for the annual congress of the <strong>European</strong> Hemato<strong>lo</strong>gy Associat<strong>io</strong>n | 2011; 5(1) | 339 |