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Most COVID-19 vaccines are designed to elicit immune responses, ideally neutralizing antibodies (NAbs), against the SARS-CoV-2 spike protein. Several vaccines, including mRNA, adenoviral-vectored, protein subunit and whole-cell inactivated virus vaccines, have now reported efficacy in phase III trials and have received emergency approval in many countries.

Human adenosine deaminases (ADAs) modulate the immune response: ADA1 via metabolizing adenosine, a purine metabolite that inhibits pro-inflammatory and Th1 cytokine production, and the multi-functional ADA2, by enhancing T-cell proliferation and monocyte differentiation. Newborns are relatively deficient in ADA1 resulting in elevated plasma adenosine concentrations and a Th2/anti-inflammatory bias compared to adults.

In addition to providing pathogen-specific immunity, vaccines can also confer nonspecific effects (NSEs) on mortality and morbidity unrelated to the targeted disease. Immunisation with live vaccines, such as the BCG vaccine, has generally been associated with significantly reduced all-cause infant mortality. In contrast, some inactivated vaccines, such as the diphtheria, tetanus, whole-cell pertussis (DTPw) vaccine, have been controversially associated with increased all-cause mortality especially in female infants in high-mortality settings.

The BCG vaccine has long been recognized for reducing the risk to suffer from infectious diseases unrelated to its target disease, tuberculosis. Evidence from human trials demonstrate substantial reductions in all-cause mortality, especially in the first week of life. Observational studies have identified an association between BCG vaccination and reduced risk of respiratory infectious disease and clinical malaria later in childhood.

Baseline signatures might contribute to identifying interventional targets to be modulated prior to vaccination in order to improve vaccination responses

The textbook view of vaccination is that it functions to induce immune memory of the specific pathogen components of the vaccine, leading to a quantitatively and qualitatively better response if the host is exposed to infection with the same pathogen

We describe here the effects of treatment with interferon-α2b in a cohort of confirmed COVID-19 cases in Wuhan, China

Protection may be further improved by integrating these approaches, namely vaccinating the neonate under the cover of vertically transferred maternal immunity

Implementation of lifelong ART of all HIV-infected women has the potential to improve maternal determinants of protective immunity in the young infant

Immunity is distinct in early life and greater precision is required in our understanding of mechanisms of early life protection to inform development of new pediatric vaccines