Nature Of, Immune Reaction and Side Effects of COVID-19 Vaccines: Synthesis of Information from Ten Phase II Trials for Planning Vaccination Programmes

Abstract

Background: Phase III clinical trials reporting the efficacy and safety of covid-19 vaccines are awaited with optimism about their ability to prevent infection, transmission and mortality/morbidity. Phase II trials results indicate what they might show.Methods: We identified published and pre-print results of phase II covid-19 vaccine trials synthesising data about the vaccines, trial designs, efficacy and safety. We extracted details on trial characteristics, participant details, immunogenicity and adverse effect outcomes focusing on the dose producing the largest immune response.Results: We found ten publications describing Covid-19 vaccine trials. Eight were randomised controlled trials. Vaccination was by intramuscular injection of either inactivated SARS-CoV-2, genetically engineered virus, genetically engineered RNA or protein. One trial used the meningococcal vaccine as a control. Trials recruited 20 to 1,077 participants, totaling 3983, the largest trial having 634 in the intervention arm. Participants were mostly aged between 18 and 60 years, and the (mean or median) age between 26.4 and 43.5-years with no participants under 18-years and few over 80-years. All vaccines produced neutralising antibodies and T-cell responses (when measured). Side effects included fatigue, localised pain, muscle-ache, fever and feeling feverish. These symptoms were more common in covid-19 vaccine recipients compared with controls. In the largest study, compared with meningococcal vaccine as control, 70% of participants reported post-vaccination fatigue (48% in controls), 68% headache (38%), 60% muscle ache (25%), 18% fever (Discussion: People under 18-years and few over 80-years are not represented in these trials. The immune response is generally vigorous. Mild-moderate grade adverse effects mimicking covid-19 are common, with implications for the anticipated vaccination programmes, including distinguishing covid-19 and post-vaccine symptoms.