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. 2022 Jun 30;95(2):221–235.

Table 2. A Snapshot of the Research in Time of Vaccination.

Type of vaccine, Year of publication, country Setting/methods Main findings Conclusion Ref
►Hepatitis A vaccine
►Influenza vaccine 2008, UK
Setting: Observational
►Types of vaccine: hepatitis A vaccine (HAVRIX; Glaxo SmithKline) and Influenza vaccine (the trivalent vaccine consisted of three antigens: A/New Caledonia/20/99; A/Panama/2007/99; and B/Shangdong/7/97).
►Types of vaccine administration: intramuscular injection.
►Data from two studies that examined morning versus afternoon vaccination.
►In the first study, 75 university students (34 men; mean age of 22.9 years) were randomly allocated to either a morning (10 a.m. to 12 p.m.; n=39) or early evening (4 p.m. to 6 p.m.; n=36) hepatitis A vaccination session.
►In the second study, influenza vaccine was administered to 89 (38 men) older (aged 65 years or older) community-based adults. Fifty-nine participants vaccinated in the morning between 8 a.m. and 11 a.m., and 30 in the afternoon between 1 p.m. and 4 p.m. Participants vaccinated between 11 a.m. and 1 p.m. were excluded.
►In both studies the anti-HAV and anti-influenza antibody titers were measured approximately 1 month after vaccination.
►Participants responded with a significant increase in antibody titer for all four antigens from baseline to 1 month.
►Vaccinated in the morning in men, but not women, mounted antibody response to both HAV and the influenza strains.
►Diurnal vaccination enhance hormonal immune response following vaccination. [24]
►Influenza vaccine 2016, UK Setting: cluster-randomized trial
►Types of vaccine: Trivalent Influenza vaccine
►Types of vaccine administration: intramuscular injection.
►A cluster-randomized trial was designed to evaluate morning versus afternoon vaccination (either 9 and 11 am or 3 and 5 pm) among 276 adults (aged 65+ years) following influenza vaccination.
►One month after vaccination, the anti-influenza antibody titers, serum cytokines IL-6 and IL-10 and seven steroids in serum (cortisol, cortisone, corticosterone, 11-deoxycortisol, testosterone, dehydroepiandrosterone (DHEA) and androstenedione) were measured.
►Greater antibody response was detected in those individuals who vaccinated in the morning than afternoon vaccination.
►Cytokines and steroid hormones were not related to antibody responses.
►Morning vaccination in older adults may be beneficial for the influenza antibody response. [25]
►Influenza vaccine 2017, USA Setting: Observational
►Types of vaccine: Trivalent Influenza vaccine
►Types of vaccine administration: intramuscular injection.
►A 5-year study to assess immune responses to the influenza A in 114 samples from younger (30–40-year-old) and 165 samples from aged (>65-year-old) individuals who vaccinated in the morning versus afternoon.
►Antibody responses, B cell subset distribution in blood and the blood transcriptome were analyzed before and after vaccination.
►Timing of vaccination did not affect immune response in younger and aged individuals.
►The time of sample collection effect on the numbers of some of the B cell subsets in blood and global gene expression of whole blood samples.
►The time of sample collection effect on the results of immunological factors following influenza vaccination. [26]
►BCG 2020, Western European countries Setting: Interventional and cohort
►Types of vaccine: BCG vaccine
►Types of vaccine administration: Intradermal injection.
►BCG vaccine was administered in at 6 pm and 6:30 pm (n=18; mean age of 25.8 SD=10.7 years; 61% females) compared with 36 age- and sex-matched volunteers with vaccinated between 8 am and 9 am.
►Peripheral blood mononuclear cells (PBMCs) were stimulated with Staphylococcus aureus and Mycobacterium tuberculosis before, as well as 2 weeks and 3 months after BCG vaccination and Cytokine production was measured in response to stimulation.
►Also, an independent cohort of 302 individuals vaccinated between 8 am and 12 pm with BCG in order to assess influence of vaccination time on induction of trained immunity.
►Morning vaccination elicited a stronger trained immunity and adaptive immune phenotype compared with evening vaccination (eg, specific M. tuberculosis IFN-γ responses were significantly higher in morning-vaccinated individuals 3 months after BCG vaccination compared with evening vaccination).
►In a large cohort of 302 volunteers, early morning vaccination resulted in a superior cytokine production capacity compared with later morning.
►BCG vaccination in the morning induces stronger trained immunity and adaptive responses compared with evening vaccination. [27]
►Hexavalent vaccine 2019, Germany Setting: Randomized Controlled Trial
►Types of vaccine: Hexavalent vaccine
►Types of vaccine administration: Intramuscular injection.
►Twenty-six infants born at 26–30 weeks’ gestation received their first routine hexavalent vaccination in the morning (7 and 10 a.m.) versus evening (7 and 10 p.m.).
►Pulse oximeter saturation, actigraphy, and rectal temperature were obtained for 24 h before and after vaccination. Antibody titers were measured before and 24 h after vaccination to determine inflammatory markers.
►Antibody titers for Bordetella pertussis were increased in both groups, but there was no difference in inflammatory markers 24 h after vaccination.
►Vaccination led to an increase body temperature and cardiorespiratory event rate (CER) in both groups, but there was no significant difference between the morning and evening groups.
►The study did not identify a difference in CER between morning and evening vaccination. [28]
►SARS-CoV-2 inactivated vaccine 2021, China Setting: Prospective cohort study
►Types of vaccine: inactivated SARS-CoV-2 vaccine (BBIBP-CorV, Sinopharm, Beijing).
►Types of vaccine administration: Intramuscular injection.
►The dynamics of immune responses were measured among 63 healthcare workers (HCWs) who received inactivated SARS-CoV-2 vaccine in the morning (9 am–11 am, n = 33) or afternoon (15 pm–17 pm, n = 30).
►Participants vaccinated in the morning showed significantly higher level of NAbs in the sera as well as stronger B cell and Tfh responses to the vaccination.
►The percentages of antibody-secreting cells (ASCs) cells, monocytes, and dendritic cells were significantly higher in the morning vaccination group.
►These data suggest that vaccination in the morning resulted in a stronger immune response to an inactivated SARS-CoV-2 vaccine than in the afternoon. [29]
►SARS-CoV-2 mRNA (Pfizer) and Adenoviral (AstraZeneca) vaccine 2022, UK Setting: Randomized Controlled Trial
►Types of vaccine: SARS-CoV-2 mRNA (Pfizer) and Adenoviral (AstraZeneca) vaccine
►Types of vaccine administration: Intramuscular injection.
►Anti-Spike antibody levels were investigated in three times of vaccination (Time 1, 7-10:59 h; Time 2, 11-14:59 h; Time 3, 15-21:59 h), two type of vaccines (Pfizer, mRNA bnt162b2 or AstraZeneca, Adenoviral AZD1222), the age groups (16-29, 30-39, 40-49, or 50-74 years), sex, and the number of days post-vaccination.
►The anti-Spike responses were measured during the 2-10 weeks after vaccination.
►The anti-Spike responses were higher in those who were vaccinated later in the day (p = 0.013), in those who received the Pfizer mRNA vaccine (p<0.0001), in younger participants (p< 0.0001), and in women (p = 0.013).
►A significant association between days post-vaccination and vaccine type (p<0.0001) and age (p=0.032), but not with vaccine time (p=0.238) were observed.
►The results did not show a significant effect of time of day of vaccination (p=.23), day of sample collection (p = 0.097) and two time intervals (before or after 1 pm).
►Analysis of 2784 health care workers revealed a significant effect of the time of vaccination on anti-Spike antibody levels following the administration of two alternative SARS-CoV-2 vaccines (mRNA or Adenovirus based).
►The results revealed that the magnitude of the anti-Spike antibody response is associated with the multiple variables, including time of day of vaccination, vaccine type, participant age, sex, and days postvaccination. [30]

BCG: Bacillus Calmette–Guérin; CER: cardiorespiratory event ratel; HCWs: healthcare workers; Nab: neutralizing antibody; Tfh: follicular helper T; ASC: antibody-secreting cells; PBMCs: Peripheral blood mononuclear cells; TNF-α: tumor necrosis factor α; IL-1β: interleukin 1β; IFN-γ: Interferon gamma; NAbs: neutralizing antibodies; ASCs: antibody-secreting cells