Principles and Challenges in anti-COVID-19 Vaccine Development

Int Arch Allergy Immunol. 2021;182(4):339-349. doi: 10.1159/000514225. Epub 2021 Feb 1.


The number of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2)-infected patients keeps rising in most of the European countries despite the pandemic precaution measures. The current antiviral and anti-inflammatory therapeutic approaches are only supportive, have limited efficacy, and the prevention in reducing the transmission of SARS-CoV-2 virus is the best hope for public health. It is presumed that an effective vaccination against SARS-CoV-2 infection could mobilize the innate and adaptive immune responses and provide a protection against severe forms of coronavirus disease 2019 (COVID-19) disease. As the race for the effective and safe vaccine has begun, different strategies were introduced. To date, viral vector-based vaccines, genetic vaccines, attenuated vaccines, and protein-based vaccines are the major vaccine types tested in the clinical trials. Over 80 clinical trials have been initiated; however, only 18 vaccines have reached the clinical phase II/III or III, and 4 vaccine candidates are under consideration or have been approved for the use so far. In addition, the protective effect of the off-target vaccines, such as Bacillus Calmette-Guérin and measles vaccine, is being explored in randomized prospective clinical trials with SARS-CoV-2-infected patients. In this review, we discuss the most promising anti-COVID-19 vaccine clinical trials and different vaccination strategies in order to provide more clarity into the ongoing clinical trials.

Keywords: Bacillus Calmette-Guérin; Clinical trials; Coronavirus disease 2019; Measles; Severe acute respiratory syndrome coronavirus 2; Vaccine.

Publication types

  • Review

MeSH terms

  • COVID-19 / immunology
  • COVID-19 / prevention & control*
  • COVID-19 / virology
  • COVID-19 Vaccines* / administration & dosage
  • COVID-19 Vaccines* / immunology
  • Clinical Trials as Topic / methods*
  • Humans
  • Research Design*
  • Vaccination / methods*


  • COVID-19 Vaccines