Since its emergence in November 2019, the novel severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has spread across the world and caused significant public health and socioeconomic implications. The unprecedented impact of the COVID-19 pandemic inspired scientists the world over to design and develop effective vaccines to offer protection against the virus and contain infection.
The Pfizer vaccine was the first vaccine to be given Emergency Use Authorization in December 2020, and the Moderna vaccine was approved by the FDA a week later. Both these vaccines are messenger RNA (mRNA) vaccines and have an estimated efficacy rate of over 94%.
Iranian researchers recently provided a review of the attempts made to develop safe SARS-CoV-2 vaccines. The researchers outlined potential challenges and concerns, including disease enhancement, virus mutation, and public acceptability. Their work is published in the journal Immunological Investigations.
COVID-19 vaccine hesitancy and acceptance issues
COVID vaccine hesitancy exists among a segment of the population due to many reasons, including anti-vaccination rhetoric propagated on social media, the rapidity of vaccine approval, safety concerns about the vaccines, and the speed of vaccine development. There are also concerns about the design of some vaccines like the adenovirus vaccines, where preexisting immunity to adenoviruses may elicit a reduced immune response to the adenovirus vectors.
These factors may lead to refusal to accept vaccines by the public in the future. Thus, it is vital to establish trust and openly communicate vaccine-related information, safety, and efficacy data, and data on reported adverse events to maintain public faith in the healthcare system.
SARS-CoV-2 mutations are a challenge to global immunization efforts
The SARS-CoV-2 genome has been undergoing mutations resulting in more infectious variants with different levels of pathogenicity. Some of these variants, such as the UK (B.1.1.7), South Africa (B.1.351), and Brazil (P.1) variants are more transmissible and cause more severe disease compared to the original virus.
The emergence of new variants may reduce the effectiveness of currently available vaccines, and a need to update these vaccines may arise in the future to target the mutated epitopes of the variants.
Since mutations can only happen in replicating viruses, rapid global immunization that can effectively control the original SARS-CoV-2 virus replication will prevent new mutations and the emergence of dangerous viral variants.
Acute respiratory distress syndrome (ARDS) and vaccination risk
Although approximately 80% of COVID-19 patients are asymptomatic or only show minor symptoms, nearly 15% of patients develop severe respiratory conditions, and 5% experience ARDS, lung collapse, or multiorgan failure.
This severe disease is attributed to the development of neutralizing antibodies against the virus that lead to a heightened inflammatory response and “cytokine storm,” causing serious systemic manifestations such as lung injury.
This is known as antibody-dependent enhancement and is believed to occur via increased antibody-mediated virus uptake into phagocytic cells, resulting in increased infection and viral replication or inadequate levels of neutralizing antibodies to form the immune complex, resulting in increased inflammation severe disease.
Multiple studies show that a higher risk of pulmonary damage was associated with increased inflammatory pulmonary response in animal models vaccinated with SARS-CoV. Further in-depth research is needed to explain these observations.
Vaccine-related concerns may impede public health measures to combat COVID-19
Even if the COVID-19 pandemic ends before vaccines are fully distributed, the pharmaceutical industry and the global scientific community will continue developing effective vaccines in preparation for potential future SARS-CoV-2 or other related viral outbreaks.
Over 40 clinical trials on COVID vaccines are currently underway, including 10 trials at the Phase 3 stage, and many vaccines have already authorized for emergency use across the world.
It should also be noted that all vaccines approved so far are nearly 100% effective in preventing COVID-19-related mortality and are 60–95% effective against severe COVID-19. However, it will take many more months before global vaccination efforts result in universal protection against COVID-19.
The authors review many unique concerns related to the SARS-CoV-2 virus and the COVID vaccines designed so far.
Concerns about the virus and the vaccines may impede public health measures to combat COVID-19. COVID-19-related complications such as ARDS, ADE, and cytokine storm are not entirely understood yet, and research is ongoing to analyze the virus and its pathogenicity better. Hence the importance of public health measures such as social distancing, asymptomatic testing, early detection, self-isolation, and control of outbreaks needs to be constantly highlighted for the general public.