06.12.2012 Views

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

SHOW MORE
SHOW LESS

You also want an ePaper? Increase the reach of your titles

YUMPU automatically turns print PDFs into web optimized ePapers that Google loves.

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 |

Hooray! Your file is uploaded and ready to be published.

Saved successfully!

Ooh no, something went wrong!