In the year since the emergence of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and with understanding of the etiology of the coronavirus disease 2019 (COVID-19) pandemic, it has become clear that most infected individuals achieve some form of immunity against the virus with relatively few reported reinfections. A number of vaccines have already achieved emergency use authorization based on data from large phase 3 field efficacy clinical trials. However, our knowledge about the extent and durability of this immunity, and the breadth of vaccine coverage against SARS-CoV-2 variants is still evolving. In this narrative review, we summarize the latest and rapidly developing understanding of immunity to SARS-CoV-2 infection, including what we have learned about the key antigens of SARS-CoV-2 (i.e., the spike protein and its receptor-binding domain), their importance in vaccine development, the immediate immune response to SARS-CoV-2, breadth of coverage of emerging SARS-CoV-2 variants, contributions of preexisting immunity to related coronaviruses, and duration of immunity. We also discuss lessons from newer approaches, such as systems serology, that provide insights into molecular and cellular immune responses elicited and how they relate to the trajectory of infection, and potentially inform immune correlates of protection. We also briefly examine the limited research literature on immune responses in special populations, such as pregnant women and children.

Invasive meningococcal disease (IMD) caused by the bacteria Neisseria meningitidis is rare but potentially fatal. For healthy adolescents, the US Advisory Committee on Immunization Practices (ACIP) recommends routine vaccination with MenACWY and recommends MenB vaccination under shared clinical decision-making (previously "Category B"). The recommendation for MenB vaccination was the first category B recommendation in adolescents, and it is unclear how healthcare providers (HCPs) implement these guidelines. This 2017 web-based survey of US HCPs explored characteristics associated with prescribing or receiving MenB and MenACWY vaccines, HCP knowledge of vaccine recommendations, and real-world practice patterns. Of 529 respondents, 436 prescribed MenB vaccines to their eligible adolescent/young adult patients and 93 prescribed MenACWY vaccines only. MenB vaccine prescribers were more likely to be pediatricians compared with MenACWY vaccine only prescribers, and patients who received MenB vaccines were more likely to be non-Hispanic whites living in shared spaces (eg, college dormitories) than those not receiving the vaccine. Seventy-seven percent of HCPs indicated that they prescribe MenACWY vaccines consistently with ACIP recommendations (to all members of an age group), whereas only 7% indicated that they prescribe MenB vaccines consistently with ACIP recommendations (individual clinical decision making). Patientrelated factors, disease-related factors, and guidelines all influenced HCP decisions to prescribe meningococcal vaccines. Providing HCPs with clear guidance on how to initiate discussion of MenB vaccines with patients and their caregivers may aid in fully protecting US adolescents against meningococcal disease caused by 5 of the disease-causing serogroups. ARTICLE HISTORY

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Background Meningococcal serogroup B (MenB) is the most common cause of invasive meningococcal disease (IMD) in the United States. The US Advisory Committee on Immunization Practices (ACIP) recommends vaccination of healthy adolescents against MenB based on shared clinical decision-making (Category B recommendation). This survey assessed factors associated with MenB vaccine awareness, utilization, and interest among parents/guardians of US adolescents. Methods Survey participants were identified in 2016 through KnowledgePanel®, an online random sample of US households; population-based weighting methodology was used to ensure data reflected a demographically representative population sample. Adults with ≥1 dependent aged 16–19 years were eligible and completed an online questionnaire. Respondents were grouped in terms of MenB vaccination of their child as: 1) vaccinated, 2) intending to vaccinate, 3) MenB vaccine-unaware, or 4) vaccine-aware but not intending to vaccinate. Univariate and multivariate analyses were used to identify factors influencing MenB vaccine awareness and utilization; univariate analyses used the weighted proportion of each group or weighted means, and multivariate analyses used logistic regression models based on the weighted study sample of each group. Results Six hundred nineteen parents/guardians participated, corresponding to 26,266,700 members of the US population after weighting. MenB vaccine awareness was significantly associated with parent race and sex. Specifically, 57% of parents were unaware of MenB vaccines, and there was significantly higher lack of awareness among males and those of Hispanic or non-White ethnicity. In addition, 36% of unaware parents/guardians were interested in and seeking MenB vaccine information from their healthcare provider (HCP), and there was higher interest among parents of Hispanic ethnicity. ‘Vaccinated/intending to vaccinate’ versus ‘not intending to vaccinate’ and ‘vaccinated’ versus ‘intending to vaccinate’ were both strongly associated with whether an HCP had recommended vaccination (odds ratios, 4.81 [95% CI 2.46, 9.35] and 5.66 [95% CI 2.46, 12.87], respectively). Conclusions Racial and socioeconomic disparities exist in the awareness and utilization of MenB vaccines among parents/guardians of US adolescents. HCP discussion and recommendation are critical catalysts for MenB vaccination and underscore the need to accurately interpret and implement the shared clinical decision-making (Category B) recommendation.

Influenza is a common respiratory infection associated with a substantial clinical, humanistic, and economic burden globally. Vaccines are essential to prevent and control influenza and are recommended by public-health agencies, such as the WHO and US CDC; however, vaccination rates vary considerably across the globe. This review aimed to investigate the perceived barriers and attitudes to influenza vaccination in the global population, in order to identify strategies that may improve influenza vaccination coverage. A structured literature search was undertaken to identify studies that reported on patient-reported attitudes towards influenza vaccination, focused on the adult general population in 16 prespecified countries. Eighty studies were included in this review. Negative attitude towards healthcare were found to be the most agreed upon barrier to vaccine uptake (31.1% agreement). The most agreed promoter of influenza vaccination was trust in healthcare services (62.0% agreement). Approximately 50% of participants intended to receive the influenza vaccine in the following season. To improve influenza vaccination coverage, healthcare workers must strengthen the foundation of substantial trust in healthcare services and provide educational materials that improve influenza vaccination knowledge among the adult general population.