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Background: Vaccination of pregnant people with a vaccine containing acellular pertussis (tetanus–diphtheria–acellular pertussis [Tdap]) has been recommended in Canada since 2018, and the evaluation of delivery models for efficient maternal Tdap administration is a priority for the Quebec Ministry of Health. We implemented 3 vaccine delivery models, in addition to the existing standard of practice model, and compared the vaccine coverage achieved by the 4 models in Quebec. Methods: In this quasiexperimental, multicentre observational study, we recruited pregnant people at less than 21 weeks’ gestation in 4 Quebec regions from April to October 2019. We compared 4 vaccine delivery models: local community service centres (centre local de services communautaires [CLSCs], baseline), family medicine groups (FMGs), obstetrics clinic and the oral glucose challenge test (OGCT). In addition to the CLSCs, 3 FMGs, 1 obstetric clinic and a hospital-based OGCT screening program participated. We determined vaccination status from a self-reported questionnaire, the Quebec Immunization Registry or medical charts. We compared model-specific (for participants recruited to a model and subsequently vaccinated within that model) and overall vaccine coverage (considering all vaccine delivery pathways) and used logistic regression to adjust for sociodemographic variables. Results: Overall, 946 of 1000 recruited pregnant people were eligible for analyses. Vaccination via the FMGs achieved the highest model-specific vaccine coverage (67.8%, 95% confidence interval [CI] 60.5%–74.4%), but coverage was not significantly different from the CLSCs (63.8%, 95% CI 57.6%–69.6%). For overall vaccine coverage, the FMG (86.5%, 95% CI 80.6%–90.9%) and obstetrics models (85.9%, 95% CI 80.9%–89.7%) achieved significantly higher vaccine coverage than the CLSCs (66.3%, 95% CI 60.1%–71.9%). The OGCT model did not improve overall vaccine coverage (61.8%, 95% CI 56.1%–67.2%). Interpretation: Compared with CLSCs, overall vaccine coverage was higher when Tdap was offered in FMGs or an obstetrics clinic providing prenatal care. Health professionals involved in pregnancy follow-up recommending and offering the vaccine may be a key factor in optimizing vaccine coverage.

Background In Canada, vaccination against pertussis (Tdap) during pregnancy has been recommended since 2018, with suboptimal uptake. We aimed to assess the determinants of intention and uptake of Tdap vaccine among pregnant women in Quebec. Methods Participants ( 35 weeks). One measured vaccination intention and the other assessed the actual decision. Questionnaires were informed by the Theory of Planned Behaviour (TPB). We used logistic multivariate analysis to identify determinants of Tdap vaccination uptake during pregnancy using responses to both questionnaires. Results A total of 741 women answered the first survey and 568 (76.7%), the second survey. In the first survey most participants intended to receive the Tdap vaccine during their pregnancy (76.3%) and in the second survey, 82.4% reported having been vaccinated against Tdap during their pregnancy. In multivariate analysis, the main determinants of vaccine uptake were: a recommendation from a healthcare provider (OR = 7.6), vaccine intention (OR = 6.12), social norms (or thinking that most pregnant women will be vaccinated (OR = 3.81), recruitment site (OR = 3.61 for General Family Medicine unit) perceived behavioral control (or low perceived barriers to access vaccination services, (OR = 2.32) and anticipated feeling of guilt if not vaccinated (OR = 2.13). Safety concerns were the main reason for not intending or not receiving the vaccine during pregnancy. Conclusion We observed high vaccine acceptance and uptake of pertussis vaccine in pregnancy. The core components of the TPB (intention, social norms and perceived behavioral control) were all predictors of vaccine uptake, but our multivariate analysis also showed that other determinants were influential: being sufficiently informed about Tdap vaccination, not having vaccine safety concerns, and anticipated regret if unvaccinated. To ensure high vaccine acceptance and uptake in pregnancy, strong recommendations by trusted healthcare providers and ease of access to vaccination services remain instrumental.

To estimate the risk of recurrence of adverse events following immunization (AEFIs) upon revaccination and to determine among patients with suspected vaccine allergy whether allergy skin test positivity was associated with AEFI recurrence.This prospective observational study included patients assessed in the Canadian Special Immunization Clinic Network from 2013 to 2019 with AEFIs who required revaccination with the vaccine temporally associated with their AEFI. Participants underwent standardized assessment and data collection. Special Immunization Clinic physicians used guidelines to inform their recommendations. Participants were followed up after revaccination to capture AEFI recurrences. Data were transferred to a central database for descriptive analysis.Overall, 588 participants were assessed for 627 AEFIs; 570 (91%) AEFIs occurred in children18 years of age. AEFIs included immediate hypersensitivity (130/627; 21%), large local reactions (110/627; 18%), nonurticarial rash (51/627; 8%), seizures (26/627; 4%), and thrombocytopenia (11/627; 2%). Revaccination was recommended to 513 of 588 (87%) participants. Among participants recommended and due for revaccination during the study period, 63% (299/477) were revaccinated. AEFI recurrence was 10% (31/299) overall, 31% (15/49) for large local reactions, and 7% (5/66) for immediate hypersensitivity. No recurrence was serious. Among 92 participants with suspected vaccine allergy who underwent skin testing and were revaccinated, the negative predictive value of skin testing for AEFI recurrence was 96% (95% CI 92.5%-99.5%).Most individuals with AEFIs were safely revaccinated. Among those with suspected vaccine allergy, skin testing may help determine the safety of revaccination.

Background and objectives Safety and effectiveness concerns may preclude physicians from recommending vaccination in mild/moderate inborn errors of immunity (IEI). This study describes attitudes and practices regarding vaccination among physicians who care for patients with mild/moderate B cell or mild/moderate combined immunodeficiencies (CID) and vaccination completeness among patients diagnosed with IEIs. Methods Canadian physicians caring for children with IEI were surveyed about attitudes and practices regarding vaccination in mild/moderate IEI. Following informed consent, immunization records of pediatric patients with IEI evaluated before 7 years of age were reviewed. Vaccine completeness was defined at age 2 years as 4 doses of diphtheria-tetanus-pertussis (DTaP), 3 doses pneumococcal conjugate (PCV), and 1 dose measles-mumps-rubella (MMR) vaccines. At 7 years 5 doses of DTP and 2 doses MMR were required. Results Forty-five physicians from 8 provinces completed the survey. Most recommended inactivated vaccines for B cell deficiency: (84% (38/45) and CID (73% (33/45). Fewer recommended live attenuated vaccines (B cell: 53% (24/45), CID 31% (14/45)). Of 96 patients with IEI recruited across 7 centers, vaccination completeness at age 2 was 25/43 (58%) for predominantly antibody, 3/13 (23%) for CID, 7/35 (20%) for CID with syndromic features, and 4/4 (100%) for innate/phagocyte defects. Completeness at age 7 was 15%, 17%, 5%, and 33%, respectively. Conclusion Most physicians surveyed recommended inactivated vaccines in children with mild to moderate IEI. Vaccine completeness for all IEI was low, particularly at age 7. Further studies should address the reasons for low vaccine uptake among children with IEI and whether those with mild-moderate IEI, where vaccination is recommended, eventually receive all indicated vaccines.

The objective of this retrospective study was to assess protection against vaccine preventable diseases (VPDs) in children treated for acute lymphoblastic leukemia (ALL).Clinical characteristics and vaccination records were collected. Antibodies against VPDs were measured after completion of chemotherapy and after a booster dose of vaccine. Immunization status of household members was evaluated.Sixty children were included. Median interval between the end of chemotherapy and enrolment in the study was 13 months (range 1-145). At ALL diagnosis, 81.3% of the children were up to date with their vaccination schedule. This proportion decreased to 52.9% at enrolment. Among the parents, 21% were up to date with their immunization schedule and 42% had received seasonal influenza vaccination. After chemotherapy, less than 50% of the patients were seroprotected against tetanus, diphtheria, polio 3, Haemophilus influenzae type b (Hib), and mumps and no more than 80% were seroprotected against polio 1 and 2, measles, rubella, and varicella. After a booster dose of vaccine, the rate of protection increased to over 90% for each of the following antigens: TT, DT, polio 1, Hib, measles, and rubella. Nevertheless, polio 3, mumps, and varicella-zoster virus antibodies titers/concentrations remained below seroprotective thresholds in over 20% of the patients.After chemotherapy for ALL, most of the children were not protected against VPDs. As the majority mounted a robust response to booster vaccines, efforts need to be done to improve protection against VPDs by implementing a systematic vaccine booster schedule. This could also be helped by reinforcing household members' immunization.

Since the introduction of the varicella vaccine to the routine immunization schedule, we have observed a 70% reduction in the rate of varicella-associated invasive group A streptococcal infections (IGASI). In the mean time, the clinical presentation of IGASI and microbiological characteristics of GAS strains have changed significantly.

Prevention of cytomegalovirus (CMV) disease with ganciclovir has led to decrease morbidity and mortality in hematopoietic stem cell transplant (HSCT) recipients. In the present report, we describe a case of ganciclovir treatment failure in a HSCT child who presented a refractory CMV infection despite harbouring a susceptible strain. The failure was partly attributed to sub-therapeutic plasma ganciclovir levels. Our experience emphasizes the importance of drug monitoring in immunocompromised patients.