Upon exposure to vaccine-preventable diseases, certain individuals are at increased risk for complications due to preexisting diseases, age or immunosuppressive treatment. Vaccination against influenza, pneumococcal disease and hepatitis B (for some groups) is advised in addition to standard vaccination against diphtheria, tetanus and pertussis. We estimated the vaccination coverage and determinants of recommended vaccinations in patients with diabetes mellitus type 1 (n = 173) and type 2 (n = 177), chronic kidney disease (CKD) (n = 138), heart failure (n = 200), chronic obstructive pulmonary disease (COPD) (n = 187), HIV (n = 201) or solid organ transplantation (SOT) (n = 201) in a monocentric study. Vaccination data were retrieved from documents provided by patients and general practitioners, and from the Flemish vaccination register. Less than 10% had received all recommended vaccines. Overall, 29% of subjects were vaccinated against diphtheria-tetanus, 10% against pertussis, 44% against influenza, 32% against pneumococcal disease and 24% of HIV patients and 31% of CKD patients against hepatitis B. Age was positively associated with vaccination against influenza (OR:2.0, p < .01) and pneumococcal disease (OR:2.6, p < .001). Patients with COPD, HIV and SOT were more likely to be vaccinated against influenza (OR:2.8, p < .001, OR:1.8, p < .05; OR:2.0, p < .001, respectively) and pneumococcal disease (OR:2.9, p < .001, OR:25.0, p < .001; OR:2.6, p < .001, respectively) than patients with heart failure. Reason for non-vaccination were concerns about effectiveness, necessity and side effects of influenza vaccines, and not being aware of the recommendation for pneumococcal disease. Initiatives to monitor the vaccination status of vulnerable patients are needed, which is why we advocate systematic vaccination registration and frequent communication about vaccination.

Background: The burden of human papillomavirus (HPV) in human immunodeficiency virus (HIV)-infected persons and solid organ transplant (SOT) recipients is high. Clinical trials on HPV vaccines in persons living with HIV and particularly in SOT recipients have been sparse to date, included low numbers of participants, and none of them assessed the 9-valent HPV (9vHPV) vaccine. We investigated the immunogenicity with respect to HPV types 6, 11, 16, 18, 31, 33, 45, 52, and 58 and the safety of the 9vHPV vaccine in persons living with HIV and recipients of a kidney, lung, or heart transplant. Methods: This is a phase III investigator-initiated study in 100 persons living with HIV (age 18–45 years) and 171 SOT recipients (age 18–55 years). The 9vHPV vaccine was administered at day 1, month 2, and month 6. Primary outcome was seroconversion rates to the 9vHPV types at month 7. Secondary outcomes were geometric mean titers (GMTs) and frequency of adverse events (AEs). Results: All HIV-infected participants seroconverted for all HPV types, but seroconversion ranged from 46% for HPV45 to 72% for HPV58 in SOT recipients. GMTs ranged from 180 to 2985 mMU/mL in HIV-positive participants and from 17 to 170 mMU/mL in SOT recipients, depending on the HPV type. Injection-site AEs occurred in 62% of participants but were mostly mild or moderate in intensity. None of the reported serious adverse events were deemed vaccine related. No patients died during the study. Conclusions: Immunogenicity of the 9vHPV vaccine is high in persons living with HIV but suboptimal in SOT recipients. The vaccine is safe and well tolerated in both groups.

Patients with chronic diseases are at increased risk of complications following infection. It remains, however, unknown to what extend they are protected against vaccine-preventable diseases. We assessed seroprevalence of antibodies against diphtheria, tetanus and pertussis to evaluate whether current vaccination programs in Belgium are adequate. Antibody titers were assessed with a bead-based multiplex assay in serum of 1052 adults with chronic diseases. We included patients with diabetes mellitus type 1 (DM1) (n = 172), DM2 (n = 77), chronic kidney disease (n = 130), chronic obstructive pulmonary disease (COPD) (n = 170), heart failure (n = 77), HIV (n = 196) and solid organ transplant (SOT) recipients (n = 230). Factors associated with seroprevalence were analysed with multiple logistic regression. We found seroprotective titers in 29% for diphtheria (≥0.1 IU/mL), in 83% for tetanus (≥0.1 IU/mL) and 22% had antibodies against pertussis (≥5 IU/mL). Seroprotection rates were higher (p < 0.001) when vaccinated within the last ten years. Furthermore, diphtheria seroprotection decreased with age (p < 0.001). Tetanus seroprotection was less reached in women (p < 0.001) and older age groups (p < 0.001). For pertussis, women had more often a titer suggestive of a recent infection or vaccination (≥100 IU/mL, p < 0.01). We conclude that except for tetanus, the vast majority of at-risk patients remains susceptible to vaccine-preventable diseases such as diphtheria and pertussis.

Seasonal influenza is an annually recurring threat to residents of long-term care facilities (LTCFs) since high age and chronic disease diminish immune response following vaccination. Although immunization of healthcare workers (HCWs) has proven to be an added value, coverage rates remain low. A ready-to-use instruction manual was designed to facilitate the implementation of interventions known to increase vaccination coverage in healthcare institutions. It includes easy-access vaccination, role model involvement, personalized promotional material, education and extensive communication. We evaluated this manual during the 2017-vaccination campaign in 11 LTCFs in Belgium. Vaccination coverage before and after the campaign was recorded by the LTCFs and the usefulness of the manual was assessed by interviewing the organizers of the local campaigns. Attitudes toward vaccination and reasons for vaccination were evaluated with a quantitative survey in HCWs before and after the campaign. The mean vaccination coverage reported by the LTCFs was 54% (range: 35–72%) in 2016 and 68% (range: 45–81%) in 2017. After the campaign, HCWs were less likely to expect side effects after influenza vaccination (OR (95%CI): 0.4 (0.2–0.9)) or to oppose vaccination (OR (95%CI): 0.3 (0.1–0.9)). The majority (>60%) indicated to be well informed about the risks of influenza and the efficacy of the vaccine. The main reason for vaccination in those who previously refused it was resident protection. The manual was found useful by the organizers of the campaigns. We conclude that the use of an intervention manual may support vaccination uptake and decrease perceived barriers toward influenza vaccination in countries without mandatory vaccination in HCWs.