Safety and Efficacy of the Common Vaccines against COVID-19

Abstract

The worldwide pandemic of coronavirus disease 2019 (COVID-19) has imposed a challenge on human health worldwide, and vaccination represents a vital strategy to control the pandemic. To date, multiple COVID-19 vaccines have been granted emergency use authorization, including inactivated vaccines, adenovirus-vectored vaccines, and nucleic acid vaccines. These vaccines have different technical principles, which will necessarily lead to differences in safety and efficacy. Therefore, we aim to implement a systematic review by synthesizing clinical experimental data combined with mass vaccination data and conducting a synthesis to evaluate the safety and efficacy of COVID-19 vaccines. Compared with other vaccines, adverse reactions after vaccination with inactivated vaccines are relatively low. The efficacy of inactivated vaccines is approximately 60%, adenovirus-vectored vaccines are 65%, and mRNA vaccines are 90%, which are always efficient against asymptomatic severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection, symptomatic COVID-19, COVID-19 hospitalization, severe or critical hospitalization, and death. RNA-based vaccines have a number of advantages and are one of the most promising vaccines identified to date and are particularly important during a pandemic. However, further improvements are required. In time, all the antibody levels weaken gradually, so a booster dose is needed to maintain immunity. Compared with homologous prime-boost immunization, heterologous prime-boost immunization prompts more robust humoral and cellular immune responses.

Keywords: COVID-19; SARS-CoV-2; efficacy; prime-boost strategies; safety.

Figure 1

Illustration of the design and operation principles for different COVID-19 vaccines. Inactivated vaccines are inactivated but previously had virulent microorganisms that have been destroyed with chemicals, heat, or radiation. Adenovirus-vectored vaccines are recombinant vaccines formulated by combining the replication-deficient adenovirus vector and the target DNA. mRNA vaccines are a novel type of vaccine that works by injecting genetically engineered vectors containing RNA sequences encoding specific antigens. They function by activating cellular and humoral immunity to varying degrees.

Figure 2

Illustration of common adverse reactions induced by COVID-19 vaccines. The most common local adverse reactions are pain, redness, and swelling at the injection site, whereas the common systemic adverse reactions are fatigue, headache, and fever. Serious adverse events are very rare and typically involve thrombotic thrombocytopenia and anaphylactic reactions. The incidence of each adverse reaction is denoted by different colors and symbols, with red indicating CoronaVac, green indicating Convidecia, blue indicating BNT162b2, and ‘−’ indicating incidence is less than 10%, ‘±’ indicating incidence is 10–20%, ‘+’ indicating incidence is 20–50%, and ‘++’ indicating incidence is greater than 50%.

Figure 3

Illustration of immunogenicity induced by COVID-19 vaccines. Both neutralizing antibody and T cell responses are important in eradicating the virus and controlling COVID-19 development. Neutralizing antibodies exert effects by neutralizing free viruses. T cell responses are essential for directly killing virus-infected cells. In addition, CD4+ cell responses are critical for the cytotoxic T cell response and for antibody production in B cells. The intensity of immunogenicity is denoted by different colors and symbols, with red indicating CoronaVac, green indicating Convidecia, blue indicating BNT162b2, ‘−’ indicating the unreported intensity, ‘+’ indicating the intensity is moderate, and ‘++’ indicating the intensity is strong.