Haemophilus influenzae type b (Hib) causes many severe diseases, including epiglottitis, pneumonia, sepsis, and meningitis. In developed countries, the annual incidence of meningitis caused by bacteria is approximately 5–10 cases per population of 100,000. The Hib conjugate vaccine is considered protective and safe. Adjuvants, molecules that can enhance and/or regulate the fundamental immunogenicity of an antigen, comprise a wide range of diverse compounds. While earlier developments of adjuvants created effective products, there is still a need to create new generations, rationally designed based on recent discoveries in immunology, mainly in innate immunity. Many factors may play a role in the immunogenicity of Hib conjugate vaccines, such as the polysaccharides and proteins carrier used in vaccine construction, as well as the method of conjugation. A Hib conjugate vaccine has been constructed via chemical synthesis of a Hib saccharide antigen. Two models of carbohydrate-protein conjugate have been established, the single ended model (terminal amination-single method) and cross-linked lattice matrix (dual amination method). Increased knowledge in the fields of immunology, molecular biology, glycobiology, glycoimmunology, and the biology of infectious microorganisms has led to a dramatic increase in vaccine efficacy.

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Our previous results showed higher level of anti-Hib IgG (2.41 μg/ml) average geometric mean concentration (GMC) regardless of age and gender, followed by levels of IgM (0.91 μg/ml) and IgA (0.34 μg/ml), reflecting the prevalence of immunity against Hib. Current study was evaluated the avidity profile for these high anti-Hib concentration. The IgM avidity analysis did not revealed any significant results between male and female values. While, the average of IgA avidity in male samples were significantly (P< 0.05) higher than the average of female. Also, The result showed that high percentage of population has moderate to high IgG avidity. The study showed lower avidity percentages of both IgM and IgA comparing to IgG. More studies are suggested to be done on individuals with low avidity considering the secondary immunodeficiency in participant's history.

On 11th March 2020, the World Health Organization declared COVID-19 as a pandemic. Vaccination programs have advanced greatly in the global health period, despite widespread anti-vaccination attitudes and misinformation. Vaccine hesitancy of COVID-19 vaccine is currently a major issue in Saudi Arabia. This cross-sectional study was carried out from June 25, 2021 to October 2021 in order to investigate the knowledge levels of acceptance and hesitancy of COVID-19 vaccine among Saudi&rsquo;s nationals. The data was collected through a close-ended structured questionnaire from a total of 565 respondents. Overall, 78.41% respondents were female, 62.48% having university level education and 61.06% were unemployed. Majority of the participants 82.30% (n=465) think that Pfizer vaccine has the highest efficiency against COVID-19. Our study concludes that majority of the participants have satisfactory knowledge about COVID-19 vaccination. Concerns over vaccine components, effectiveness of vaccine and possible side effects are among the key causes for vaccine hesitancy.

In this national comprehensive seroprevalence study, indirect ELISA test was used to evaluate Haemophilus influenzae type b (Hib) anti-polyribosyl-ribitol phosphate (PRP) total antibodies (IgM, IgG, IgA) in 1,003 sera samples from routine medical check-up of healthy individuals attending the local medical facility in Jeddah, Saudi Arabia in the period from February 2014 to January 2016. Serum anti-CPS antibodies confer immunity against invasive Hib disease. An anti-CPS concentration of ⩾ 0.15 μg/mL is believed to be a serological indication for short-term immunity protection against invasive Hib disease, while a concentration of ⩾ 1.0 μg/mL is believed to be long-term protective. Results showed higher level of anti-Hib IgG (2.41 μg/ml average geometric mean concentration (GMC) regardless of age and gender, followed by levels of IgM (0.91 μg/ml) and IgA (0.34 μg/ml), reflecting the community immunity against Hib. Low anti-Hib level (< 0.15 μg/ml of anti-PRP IgG) in elderly people (males aged 57-91 years and females aged 35-64 years) may indicate a need for a booster dose of Hib vaccine to elderly people in the community. The IgG prevalence over IgM, and IgM prevalence over IgA indicate the major role of IgG over IgM and IgA in keeping immunity in the track against Hib. Low level of IgM and IgA comparing to IgG may indicate the absence of Hib acute infections in the population.