The World Health Organization has named vaccine hesitancy as one of the top ten threats to global health in 2019. The reasons why people choose not to vaccinate are complex, but lack of confidence in vaccine safety, driven by concerns about adverse events, has been identified as one of the key factors. Healthcare workers, especially those in primary care, remain key influencers on vaccine decisions. It is important, therefore, that they be supported by having easy access to trusted, evidencebased information on vaccines. Although parents and patients have a number of concerns about vaccine safety, among the most common are fears that adjuvants like aluminum, preservatives like mercury, inactivating agents like formaldehyde, manufacturing residuals like human or animal DNA fragments, and simply the sheer number of vaccines might be overwhelming, weakening or perturbing the immune system. As a consequence, some fear that vaccines are causing autism, diabetes, developmental delays, hyperactivity, and attention-deficit disorders, amongst others. In this review we will address several of these topics and highlight the robust body of scientific evidence that refutes common concerns about vaccine safety.

The coronavirus disease 2019 (COVID-19) pandemic has unleashed major and substantial changes in the provision of health care, including public health policy and the practice of medicine, and in the ways most individuals live their lives. 1 Significant changes also have occurred in vaccine development, with shortening the usual 15-to 20-year timeline to one that might be as short as 1 to 1.5 years. 2 COVID-19, the acute illness due to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), was first reported in Wuhan, Hubei province, China, in December 2019, and rapidly progressed to a global pandemic. By June 27, 2020, a total of 9.76 million people had been infected with this virus and 492 000 had died. Although widespread quarantine, isolation, and social distancing measures have, to some extent, countered the spread of SARS-CoV-2 and "flattened the curve," countries now face a multitude of challenges to the "re-opening" of society. Yet, it is clear the only way to provide effective herd immunity is with a safe and effective vaccine. With this background, the US Department of Health and Human Services (HHS) launched Operation Warp Speed-a partnership between government and industry-with the goal of delivering 300 million doses of a safe and effective vaccine by January 2021. 3 This ambitious plan initially focused on 125 potential vaccine candidates, but was rapidly narrowed to 14 candidates

Background COVID‐19 is known to cause an acute respiratory illness, although clinical manifestations outside of the respiratory tract may occur. Early reports have identified SARS‐CoV‐2 as a cause of subacute thyroiditis (SAT). Methods A systematic review was conducted in accordance with the Preferred Reporting Items for Systematic Reviews and Meta‐Analyses (PRISMA) guidelines. MEDLINE, Web of Science and PubMed databases were queried in February 2021 for studies from December 2019 to February 2021. MeSH search terms ‘COVID‐19’, ‘SARS‐CoV‐2’ and ‘coronavirus’ along with search terms ‘thyroiditis’, ‘thyrotoxicosis’ and ‘thyroid’ were used. Descriptive statistics for continuous variables and proportions for categorical variables were calculated. Results Fifteen publications reporting on 17 individual cases of COVID‐19‐induced SAT were identified. Age ranged from 18 to 69 years. The majority (14 of 17; 82%) of cases were female. The delay between onset of respiratory symptoms and diagnosis of SAT ranged from 5 to 49 days (mean, 26.5). Systemic inflammatory response syndrome related to viral infection was uncommonly reported at the time of SAT diagnosis. Thyroid ultrasonography frequently reported an enlarged hypoechoic thyroid with decreased vascularity and heterogenous echotexture. Elevated C‐reactive protein (CRP) was common at the time of SAT diagnosis, with results ranging from 4.5 to 176 mg/L (mean, 41 mg/L). Antithyroid antibodies were frequently negative. SAT‐specific treatment included corticosteroids for 12 of 17 (70.5%) patients. Most returned to normal thyroid status. Conclusion COVID‐19‐associated SAT may be difficult to identify in a timely manner due to potential absence of classic symptoms, as well as cross‐over of common clinical features between COVID‐19 and thyrotoxicosis.

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Naturally acquired immunity to malaria is robust and protective against all strains of the same species of Plasmodium. This develops as a result of repeated natural infection, taking several years to develop.