Since early last March, numerous companies have been working to develop effective vaccines against SARS-CoV-2, the virus responsible for Covid-19. Among those, Pfizer’s Comirnaty and Moderna’s Spikevax vaccines have found the greatest success, with an efficacy rate of almost 95%. The Covid-19 Dashboard on GlobalData’s Pharma Intelligence Centre tracks emerging information effectively, and in countries such as the US, Comirnaty and Spikevax were shown to lead against other Covid-19 vaccines in both contract volume and administration (see Figures 1 and 2). As of 4 July, 276 and 35 million doses of Comirnaty and Spikevax had also been administered respectively within the European Union (EU).
Despite this, new conflicting information has come out via emerging reports on EudraVigilance, the EU database used for monitoring and analysing suspected side effects. These reports indicate an increased risk in inflammation of the heart muscle (myocarditis) or membrane (pericarditis) following vaccination with either Comirnaty or Spikevax. Other known or potential side effects include asthaenia, lethargy and nocturnal hyperhidrosis for Comirnaty and anaphylaxis, delayed injection site reaction and immune thrombocytopenia for Spikevax. Both of these messenger ribonucleic acid (mRNA) vaccines also carry the risk of inducing immediate allergic reactions, usually within four hours of exposure; symptoms of these include hives, swelling or wheezing.
A safety assessment carried out by the Pharmacovigilance Risk Assessment Committee (PRAC) has confirmed an increased risk of myocarditis and pericarditis, stating that most cases occurred 14 days after vaccination, more often after the second dose and in younger adult men. As a result, both vaccines’ product information will now include details of new side effects, raising awareness of the increased risk of these disorders.
Studies have shown that vaccine acceptance has predominantly been hindered by concerns around side effects and vaccine efficacy, resulting in acceptance being below estimates required for herd immunity in many countries. As the link between Covid-19 case numbers and hospitalisations has weakened due to vaccines being administered, however, there has been recent growth in their acceptance. There may, therefore, be concerns that this new announcement will impede the usage of the Pfizer and Moderna Covid-19 vaccines, particularly at a time when many people have received the first dose but have yet to receive the second.
Despite this, the European Medical Agency (EMA) believes that the benefits of both vaccines far outweigh their risks and, as a result, there is a strong possibility that this will not impact vaccine uptake. Important is the fact that other vaccines have previously reported rare side effects, such as the AstraZeneca brand, which has been linked to a rare blood clotting disease. AstraZeneca’s vaccine has, nonetheless, remained the second most administered Covid-19 vaccine in many European countries, which suggests that this may not be a significant factor in the continued uptake of either Comirnaty or Spikevax.