Immunization of immunocompromised persons

Gaps in knowledge about the vaccine coverage of immunocompromised children: a scoping review

Immunocompromised children are at increased risk of severe illness from vaccine-preventable infections. However, inadequate vaccine coverage remains a concern. This scoping review sought to determine the current state of knowledge regarding vaccine coverage of immunocompromised children. Bibliographic databases were searched for primary research from any year. Data were analyzed quantitatively and narratively. Ninety-seven studies met inclusion criteria. The most commonly studied vaccines were pneumococcal (n = 46), influenza (n = 44), diphtheria/tetanus/pertussis/poliomyelitis/Haemophilus influenzae type B/hepatitis B-containing (n = 36), and measles- and/or mumps- and/or rubella-containing (n = 29). Immunocompromising conditions studied included cancer/stem cell transplants (n = 24), solid organ transplants (n = 23), sickle cell disease (n = 21), immunosuppressive therapy (n = 14), human immunodeficiency virus (n = 12), splenectomy (n = 4), and primary immunodeficiency (n = 2). As more children are treated with immunosuppressive therapies, it is critical to identify whether they are being appropriately vaccinated for age and condition. We identified gaps in the current state of knowledge for specific vaccine types in specific immunocompromised populations.

Zoster vaccine-associated primary varicella infection in an immunocompetent host

A 64-year-old immunocompetent man developed a widespread pruritic and vesicular rash 2 weeks after receiving the zoster vaccine (Zostavax). He had fever, bandaemia with normal total white blood cell count and mild transaminitis. PCR testing of serum and skin was positive for varicella zoster virus (VZV), while serum VZV IgG was negative. The analysis of single nucleotide polymorphism by PCR and sequencing from the skin swab was consistent with the vaccine strain. The patient received 1 week of intravenous acyclovir and was discharged after all lesions had crusted. He continues to do well on follow-up with no significant complications.

Hepatitis B immunity in the pediatric liver transplant population

PURPOSE OF REVIEW

Hepatitis B virus (HBV) infection contributes significantly to vaccine-preventable disease related deaths, and insufficient HBV immunity may have unique implications for the pediatric liver transplant population. This article reviews the significance of HBV infection and the vaccination and screening measures needed to achieve adequate HBV immunity in these children.

RECENT FINDINGS

HBV non-immunity among transplant candidates is higher than expected, even after appropriate completion of the vaccine series. Annual measurement of quantifiable HBV surface antibody in this vulnerable group should guide administration of booster and/or re-vaccination, improving immunoprotection from this potentially deadly hepatotropic virus. The liver plays a vital role in immune regulation; it induces immune tolerance and competence and both clears antigens from the circulation and generates liver-primed memory cells through antigen presentation via hepatic scavenger cells. Lymphocyte populations are depleted in patients with liver disease.

SUMMARY

Immunity provided during early childhood against HBV infection is important to both pediatric liver transplant candidates and aging recipients. Appropriate vaccination and achievement of adequate immunity pre-transplant and post-transplant is critical. The field of pediatric transplantation is ripe for functional cellular and humoral immunity studies that examine factors which predict poor immune response to childhood vaccines, particularly HBV.

Risk of Herpes Zoster and Disseminated Varicella Zoster in Patients Taking Immunosuppressant Drugs at the Time of Zoster Vaccination

OBJECTIVE

To determine the risks associated with zoster vaccine when administered to patients taking immunosuppressant medications.

PATIENTS AND METHODS

Patients enrolled in 1 of 7 managed care organizations affiliated with the Vaccine Safety Datalink between January 1, 2006, and December 31, 2009, were eligible. The exposure of interest was zoster vaccination in patients with current or remote immunosuppressant drug use. The primary outcomes were disseminated varicella zoster virus (VZV) and herpes zoster in the 42 days after vaccination. Automated data were collected on immunosuppressant drugs and baseline medical conditions. A logistic regression model using inverse probability treatment weights was used to estimate the odds of developing VZV or herpes zoster.

RESULTS

A total of 14,554 individuals had an immunosuppressant medication dispensed around the time of vaccination, including 4826 with current use and 9728 with remote use. Most patients were taking low-dose corticosteroids. No cases of disseminated VZV were found in the current or remote users. The risk of herpes zoster was elevated in the 42 days after vaccination in current vs remote users (adjusted odds ratio, 2.99; 95% CI, 1.58-5.70).

CONCLUSION

We found that patients taking immunosuppressant medications at the time of vaccination had a modest increased risk of herpes zoster in the 42 days after vaccination. The development of herpes zoster within 42 days after vaccination suggests that this is more likely due to reactivation of latent zoster virus than dissemination of the vaccine-derived varicella virus. These findings support the current zoster vaccination guidelines.

Humoral and cellular immune responses to influenza vaccination in children with cancer receiving chemotherapy

The immune response to influenza vaccination in children with cancer is controversial. The objective of this study was to characterize the cellular and humoral immune responses to an influenza vaccine in children with cancer who were receiving chemotherapy. In this study, children with cancer, who were not previously immunized, received an influenza vaccine via intramuscular injection. Blood samples were obtained prior to and at 4 weeks after immunization. Antibodies were measured using a hemagglutination inhibition (HI) assay. Cell-mediated immunity was measured by specific lymphoproliferation with (3)H-thymidine incorporation and by measuring cell frequencies following staining with monoclonal antibodies (CD8, CD4, CD19, CD45RA and CD27) using flow cytometry following incubation with the influenza antigen for 5 days. Geometric mean titers (GMT), mean counts per minute (cpm), cell frequencies prior to and following vaccination and percentage patient responses were compared using the Mann-Whitney non-parametric U and Chi-square tests; where p<0.05 was considered to indicate a statistically significant result. A total of 56 children were included. Their mean age was 6.64±3.61 years. Acute lymphoblastic leukemia (ALL) was diagnosed in 75, solid tumors in 23 and lymphoma in 2% of the children. Subjects with titers ≥40 hemagglutination units (HU) increased from 43% prior to vaccination to 73% following vaccination (p=0.01), whereas the GMT increased from 31.35 [95% confidence interval (CI), 29-111] to 143.45 HU (95% CI, 284-640) following vaccination (p<0.001). An increase in CD45RA expression in CD8(+) T cells was observed following vaccination (p=0.01). An increase in CD27 expression was observed in the CD4/8-negative cell population stimulated with the influenza antigen following vaccination (p<0.05). No serious adverse effects were observed. An increase in the seropositivity rate and GMT values following influenza vaccination were also observed. Influenza immunization was well tolerated among these children with cancer and increased the humoral and cellular immune responses with the activation of probable lymphoid precursors.

Successful serology-based intervention to increase protection against vaccine-preventable diseases in liver-transplanted children: a 19-yr review of the Swiss national reference center

As children referred for OLT in Switzerland were not vaccinated optimally, new guidelines were developed and recommended to base catch-up immunization on serum antibody titers against vaccine-preventable diseases, before and after OLT. We measure the results of this serology-based intervention by comparing vaccine coverage and antibody titers in the pre- (1990-2002, P1) and post-intervention (2003-2008, P2) cohorts in a quality control project. Forty-four P1 and 30 P2 children were evaluated. At pre-OLT visit, D, T, SPn, and MMR serologies were checked more frequently in P2 than P1 (p < 0.05). More P2 children were up-to-date for DTaP and MMR (p < 0.05) or had received ≥1 dose of HBV, HAV, SPn, and VZV vaccines (p < 0.05). One yr post-OLT, DT, SPn, MMR, and VZV serologies were more frequently checked (p < 0.05), and antibody titers were higher for DT and HAV (p < 0.05) in P2. Gender, age, or diagnosis did not explain these differences. Among P2 patients, pre- and post-OLT titers for D, T, Hib, HBV, SPn14, and SPn19 were correlated (p < 0.05 for all). Protection against vaccine-preventable diseases of high-risk children like OLT patients can be significantly improved by serology-based intervention for vaccine-preventable diseases.

Purification and characterization of a recombinant Yersinia pestis V-F1 "Reversed" fusion protein for use as a new subunit vaccine against plague

We previously developed a unique recombinant protein vaccine against plague composed of a fusion between the Fraction 1 capsular antigen (F1) and the V antigen. To determine if overall expression, solubility, and recovery of the F1-V fusion protein could be enhanced, we modified the original fusion. Standard recombinant DNA techniques were used to reverse the gene order such that the V antigen coding sequence was fused at its C-terminus to the N-terminus of F1. The F1 secretion signal sequence (F1S) was subsequently fused to the N-terminus of V. This new fusion protein, designated F1S-V-F1, was then co-expressed with the Y. pestis Caf1M periplasmic chaperone protein in BL21-Star Escherichia coli. Recombinant strains expressing F1-V, F1S-F1-V, or F1S-V-F1 were compared by cell fractionation, SDS-PAGE, Western blotting, and suspension immunolabelling. F1S-V-F1 exhibited enhanced solubility and secretion when co-expressed with Caf1M resulting in a recombinant protein that is processed in a similar manner to the native F1 protein. Purification of F1S-V-F1 was accomplished by anion-exchange and hydrophobic interaction chromatography. The purification method produced greater than 1mg of purified soluble protein per liter of induced culture. F1S-V-F1 polymerization characteristics were comparable to the native F1. The purified F1S-V-F1 protein appeared equivalent to F1-V in its ability to be recognized by neutralizing antibodies.

Influenza vaccination coverage among adult solid organ transplant recipients at three health maintenance organizations, 1995-2005

Annual immunization against influenza is recommended for solid organ transplant (SOT) recipients. We used Vaccine Safety Datalink data from 1995 to 2005 to assess influenza vaccination during the first full vaccination season (September-February) following transplant among 1800 kidney, liver, and heart transplant recipients at three health maintenance organizations. Overall, 52% of recipients were vaccinated. Older age at transplant (age 50-64 years, OR 1.81, 95% CI 1.43-2.30; age > or =65 years, OR 1.94, 95% CI 1.39-2.69), receiving vaccination in the full season pre-transplant (OR 4.54, 95% CI 3.67-5.60), and year of transplantation were significant predictors of post-transplant vaccination. Although vaccine coverage increased during study years, SOT recipients are under-immunized against influenza. Efforts to understand barriers to vaccination and increase education of physicians managing patients while awaiting and after receipt of transplant are needed.

Vaccine-induced immunity in children after orthotopic liver transplantation: a 12-yr review of the Swiss national reference center

Infections represent a significant threat in solid-organ recipients. However, a certain number of infections can be prevented by immunizing patients before their transplantation. The aim of this study is to determine the level of immunity of children undergoing liver transplantation and to assess their capacity to maintain protective levels after surgery. Charts of 44 children transplanted with deceased donation livers between 1990 and 2002 at the Children's Hospital of Geneva were reviewed. Vaccine antibody responses were established pre- and post-transplantation. Only 43% of patients were up to date for diphtheria, tetanus, acellular pertussis, and polio vaccines at the pretransplantation visit, while 44% of children older than 12 months had received their required measles-mumps-rubella vaccines. Six of 44 children had received at least one dose of hepatitis B vaccine, while only two patients had received at least one dose of hepatitis A vaccine. After immunization, and one yr after transplantation, only 14 of 44 patients had detectable anti-HBs antibodies and seven of 18 had anti-HAV antibodies. Varicella antibodies were undetectable in 15 of 19 patients immunized prior to transplantation. This study highlights the need to enforce vaccination before transplantation, follow-up on vaccine- induced immunity, and adapt vaccination schedules after liver transplantation in children, especially for non-live vaccines, which are universally recommended in this population.

Invasive pneumococcal infection presenting as septic arthritis and Austrian-like syndrome involving the tricuspid valve in a patient with underlying HIV infection

Invasive pneumococcal infection (IPI) is a re-emerging complication of Streptococcus pneumoniae infection, particularly in patients with human immunodeficiency virus (HIV) infection. We report a case of a patient who presented with pneumococcal septicaemia, meningitis and septic arthritis, which initially responded to antibiotics, but where the patient eventually succumbed to infective endocarditis of the tricuspid valve. We discuss the spectrum of clinical manifestations of IPI, focusing especially on the Austrian syndrome (defined as pneumococcal endocarditis with rupture of the aortic valve and meningitis), its association with HIV infection, and its management in light of the emergence of penicillin-resistant strains of Streptococcus pneumonia.