Background: Only a limited number of publications had evaluated the Phadiatop application for aeroallergen screen in allergic respiratory diseases (ARD) in the Chinese population. In our retrospective cohort, through studying the Phadiatop versus total IgE use in aeroallergen workups, and local aeroallergen sensitisation profiles by reviewing aeroallergen sIgE, we aimed to derive a cost-effective algorithm for ARD workup. Methods: We have retrospectively identified 694 patients with ARD in 2010-2019, and reviewed their Phadiatop test performed in our tertiary immunology laboratory. Other associated workups including total IgE, and/or allergen specific sIgE (sIgE), if available, were retrieved and analysed. Besides, a further review was performed on 53 consecutive samples collected during January 2021, for aeroallergen screening. Cost effectiveness of the existing protocol (Phadiatop screening followed by individual aeroallergen characterisation) was compared with a new testing algorithm, which started with dust mite ( Dermatophagoides pteronyssinus, Dp) allergy detection. Results: Phadiatop positivity was 67.3%, while total IgE positivity was 66.7% in the 366 patients with the test done. Overall, the agreement of these two tests was 73.5%. Asthmatic patients can be screened positive with total IgE than Phadiatop (34.9%-45.6%). Dp was the most prevalent aeroallergen (> 90%), and its sIgE level correlated best with the Phadiatop sIgE level (R = 0.99, p < 0.001). Comparing to the existing screening using Phadiatop, initial Dp detection is both sensitive and cost effective for ARD in our locality. Conclusions: Screening by Dp sIgE is as sensitive as Phadiatop in aeroallergen screen but of lower running cost. It should be the approach in our locality.

Background Safety and immunogenicity of 3 doses of BNT162b2 and CoronaVac in adult and pediatric patients with inborn errors of immunity (IEIs) remain unknown. Intradermal vaccination may improve immunogenicity in immunocompromised patients. Our study (NCT04800133) aimed to determine the safety and immunogenicity in patients with IEIs receiving a 3-dose primary series of mRNA vaccine BNT162b2 (age 12+) or inactivated whole-virion vaccine CoronaVac (age 3+) in Hong Kong, including Omicron BA.1 neutralization, in a nonrandomized manner. Intradermal vaccination was also studied. Methods Thirty-nine patients were vaccinated, including 16 with homologous intramuscular 0.3ml BNT162b2 and 17 with homologous intramuscular 0.5ml CoronaVac. Two patients received 3 doses of intradermal 0.5ml CoronaVac, and 4 patients received 2 doses of intramuscular BNT162b2 and the third dose with intradermal BNT162b2. Adverse reactions and adverse events were tracked for 7 and 28 days after each dose. Antibody responses assessed included binding IgG antibody to wild-type (WT) spike receptor-binding domain (S-RBD IgG) and surrogate neutralization activity to WT and BA.1 viruses. T cell responses were examined by intracellular cytokine staining following stimulation with SARS-CoV-2 peptide pool(s). Results No safety concerns were identified. Inadequate antibody responses were found after 2 doses in patients with humoral immunodeficiencies and especially so against BA.1. Dose 3 of either vaccine increased S-RBD IgG response. T cell responses against SARS-CoV-2 antigens were detected in vaccinated IEI patients. Intradermal third dose vaccine led to high antibody response in 4 patients. Conclusions The primary vaccination series of BNT162b2 and CoronaVac in adults and children with IEIs should include 3 doses for optimal immunogenicity.