There has been a lot of excitement around COVID-19 vaccine as the pandemic takes thousands of lives across the globe. The most cost-effective strategy to prevent infectious disease in the general population is vaccination. With the extent of fatality and economic devastation, there has been a strong push to develop COVID-19 vaccine as rapidly as possible.
Just in two months of finding the genetic sequence of Novel Coronavirus, SARS-CoV-2, vaccine candidates entered clinical development phase. It usually takes 2-3 years to complete the initial phases before any vaccine can move into this phase. This rapid development of COVID-19 vaccine depicts the gravity of the situation.
Even though COVID-19 vaccine is already in clinical development phase, healthcare professionals do not want to put all their eggs in this basket. Historically, developing vaccines for respiratory viruses have always been cumbersome. Rhinovirus, the most common cause for common cold, still does not have any vaccine. Respiratory viruses have multiple strains (Rhinovirus has around 150 strains) and sometimes these strains mutate during the breakout. New strains may start infecting people after vaccines are developed for older strains. Along with these challenges, around 200-900 million dollars are needed to bring one vaccine into the market.
As of now, we only have vaccines available for influenza virus and pneumococcal pneumonia respiratory illness. Several studies looked at the efficacy of these vaccines.
Influenza vaccine: 31% - 53% efficacy. CDC stated the efficacy as 40-60%.
Rhinovirus: Around 150 strains. No vaccines are available.
Respiratory Syncytial Virus: 39 vaccines under development
Among vaccines available for respiratory viruses, influenza has the best efficacy of around 50%. Even with this efficacy, only around 50% of the eligible US population gets vaccinated during the flu season.
The 23-valent pneumococcal vaccine that protects individuals against pneumococcal pneumonia has only 3% - 16% efficacy. Several vaccines for SARS and MERS coronaviruses were tested in the clinical trials. None of the vaccines got approval because of the safety issues. There are 39 vaccines under development for Respiratory Syncytial Virus (RSV).
Based on the existing evidence, even if COVID-19 vaccine is developed, its efficacy may not reach an impressive level. It will be highly beneficial to get the vaccine but it may not be 100% protective. All other preventive measures, including handwashing and social distancing will be just as important as vaccination.
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