I would like to thank you for subscribing to my medical blog. I hope the information I provide will be of assistance to you and your loved ones. My goal is to educate and provide guidance on maintaining your health or improving your condition if you or your family, friends and colleagues are ill or injured.
The first place I will start is with COVID. Many patients are asking about a fourth dose/second booster given that it has been several months since the first booster. Researchers are finding that our immunity to COVID begins to wane after several months, and that the booster does increase antibody levels. This is beneficial only if the quantity and quality of antibodies are able to perform the two tasks of a vaccine: preventing infection and preventing disease. At this time, there are conflicting studies where although most studies demonstrate a definite increase in antibody levels (titers), some show that rates of infection and severity of disease are decreased with the booster and others show that the antibodies are not as effective.
This disparity in studies is likely because boosters are made against the original Wuhan strain at the beginning of COVID. In other words, boosters are the same exact composition as the original two shots, with the exception being that the booster contains half the amount of vaccine. Given the virus has mutated so many times, the antibodies generated by the booster to the original strain may not be as effective against those strains that came afterwards. In fact, the Omicron variant has so many mutations that it is considered an “evolutionary leap.” Basically, this means the virus may appear different than the original strain to our immune systems, thus the antibodies from the vaccine may protect from the original strains but not the Omicron. That is likely why those receiving the booster can still get infected with the Omicron variant.
Fortunately, the Omicron variant did what viruses usually do which is to become more infectious but less virulent (less deadly). The virus has one main goal and that is to find a host to infect and set up a “replication factory” where it produces more virus to infect more hosts. However, it does not benefit the virus to be deadly, as killing the host would be counterproductive. Thus, the two best things a virus can do from an evolutionary standpoint are to become more contagious and less deadly.
Currently, a fourth vaccine is recommended for those with weakened immune systems. This includes those who are on immunosuppressants due to autoimmune conditions or organ transplant, those with cancer who are receiving chemotherapy, and those with advanced or untreated HIV infection. Both Pfizer and Moderna have submitted emergency use authorizations (EUA) to the FDA for a fourth shot (the second booster). Pfizer’s application is for those over the age of 65 given this population is more susceptible to severe disease, complications, and death. This is because the quantity and quality of human antibodies decreases with advanced age and older individuals are more likely to have comorbidities (other medical conditions) such as obesity, diabetes, hypertension, and chronic kidney disease which allow them to develop serious illness.
Moderna on the other hand, applied for a 2nd booster/fourth dose for everyone. The finding that the booster vaccine increases antibody levels and theoretically may help prevent infection and severe disease underlies the reason for the application. Again, the antibodies generated from all four doses are against that original Wuhan strain which may not be as effective against Omicron. This underlies the importance of proper data analysis. The booster vaccine requires time and large studies to answer if it is effective at preventing infection and severe disease or death in strains other than the original Wuhan strain. Currently, two Israeli studies do demonstrate efficacy, but a New England Journal of Medicine study showed no benefit from having a boost in antibodies, likely because they are effective against the original strain but not the mutated variant strains. However, with time and more studies, valuable data will be obtained which can answer this question.
Thus, at this point, a fourth dose is approved for those with decreased immunity and will likely be approved for those over age 65. It is unclear if the FDA will approve Moderna’s application for a fourth dose for everyone. The current opinion seems to be that children, teens and young to middle age adults should be fine with having the first three doses. Again, time and additional studies will tell for certain.
In either case, both Pfizer and Moderna are currently making vaccines against the Omicron variant. It is conceivable that the new variant specific COVID vaccines which are being made will be available and recommended for winter. It is possible that a new vaccine will emerge annually to cover more strains much in the same way as the annual influenza (flu) shot.
So that is where things currently stand with respect to future boosters/vaccines. I hope this helped and I will continue to update you as more information becomes available. Thank you for reading.
