COVID-19 vaccines: concerns beyond protective efficacy and safety

ABSTRACT

Introduction

Several vaccine candidates have been developed using different platforms, including nucleic acids (DNA and RNA), viral vectors (replicating and non-replicating), virus-like particles, peptide-based, recombinant proteins, live attenuated, and inactivated virus modalities. Although many of these vaccines are undergoing pre-clinical trials, several large clinical trials investigating the clinical efficacy and safety of coronavirus disease 2019 (COVID-19) vaccines have produced promising findings.

Areas covered

In this review, we provide a status update on COVID-19 vaccines currently undergoing clinical trials and discuss issues of concern beyond vaccine efficacy and safety, including dosing regimens, the mixed vaccine strategy, prior severe acute respiratory syndrome coronavirus-2 infection, antibody levels, cellular immunity and protection, variants of concern, COVID-19 vaccine distribution, vaccination willingness, herd immunity, immunity passports, and vaccine indications.

Expert opinion

Four vaccines have obtained emergency use authorization, 87 are at the clinical development stage, and 186 are in pre-clinical development. While the knowledge and development of COVID-19 vaccines is rapidly expanding, the benefits of COVID-19 vaccines must outweigh the potential risks of adverse events. To combat the COVID-19 pandemic, clinicians should consistently update COVID-19-associated information, and healthcare authorities and manufacturers should work together to provide adequate and appropriate vaccinations for the prevention of COVID-19.

Plain language summary

What is the context?

Severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) caused a global pandemic: the coronavirus disease 2019 (COVID-19) outbreak. The development and implementation of the COVID-19 vaccine could be an important measure to control the COVID-19 pandemic.

What is new?

Several phase 3 clinical trials have demonstrated the effectiveness and safety of COVID-19 vaccines for the prevention of SARS-CoV-2 infections. Several COVID-19 vaccines have obtained emergency use authorization and been implemented in many countries. Although concerns regarding unusual blood clots and low platelet counts have been raised, the benefits of COVID-19 vaccines outweigh the potential risks of adverse events.

What is the impact?

Except for children, the COVID-19 vaccine is recommended for all people, including those pregnant or immunocompromised. Healthcare authorities should advise people receiving the vaccine that they must seek medical attention if they have associated thromboembolism and thrombocytopenia symptoms. More studies are necessary to determine the appropriate vaccine dose and regimen strategy, as well as the effectiveness of COVID-19 vaccines against variants of concerns. A global effort must be made to achieve widespread vaccination and herd immunity.

KEYWORDS:

• COVID-19
• sars-cov-2
• vaccine
• protective efficacy
• safety
• cellular immunity
• variants of concern
• vaccination willingness

Article Highlights

• Four vaccines, including BNT162b2 mRNA (Pfizer/BioNTech), mRNA-1273 (Moderna), ChAdOx1 nCoV-19 (Vaxzevria, AstraZeneca), and Ad26.COV2.S (Janssen/Johnson & Johnson) have obtained emergency use authorization, and their benefits outweigh the potential risks of adverse events.

• Healthcare professionals should be alert to the signs and symptoms of thromboembolism and thrombocytopenia and advise people receiving the vaccine that they must seek medical attention if they have associated symptoms.

• The appropriate dose and regimen strategy is undergoing investigation.

• More data are required to assess the effectiveness of the COVID-19 vaccine against variants of concern.

• The successful, equitable implementation of COVID-19 vaccination requires global coordination and sustained financial, logistical, and technical support from high-income countries.

• Children and adolescents younger than 12 years of age are not authorized to receive the BNT162b2 vaccine at this time, and those younger than 18 years of age are not authorized to receive the mRNA-1273, Ad26.COV2.S, and ChAdOx1 nCov-19 vaccines.

Declaration of interest

The authors have no relevant affiliations or financial involvement with any organization or entity with a financial interest in or financial conflict with the subject matter or materials discussed in the manuscript. This includes employment, consultancies, honoraria, stock ownership or options, expert testimony, grants or patents received or pending, or royalties.

Reviewer disclosures

Peer reviewers on this manuscript have no relevant financial or other relationships to disclose.

Author contributions

All authors substantially contributed to the conception and design of the review article, the interpretation of the relevant literature and were involved in writing the review article or revising it for intellectual content.

Additional information

Funding

This study was not funded.