Third dose vaccine With BNT162b2 and its response on Long COVID after Breakthrough infections

Background: Breakthrough events are not rare after emerging of the Delta variant. On the other hand, long COVID is an unsolved issue where sufferers suffer a lot. Some study has shown that the COVID-19 vaccine has improved some clinical and libratory parameters in long COVID. But what will be the possible measures against long COVID after the breakthrough event is still a burning question. Method: We have observed the third dose by BNT162b2 in a small group(n=20) who were diagnosed as long COVID after breakthrough infections, in Sheikh Hasina National Institute of Burn & Plastic Surgery Institute, Dhaka, Bangladesh. CRP(C-reactive protein) and Anti S1 RBD IgG responses were measured. Result: All 20 participants in the study received both dosages of ChAdOx1-nCoV-19 between February 2021 to April 2021 and had breakthrough infections in the same or following month which led to long COVID syndrome. They all received a third dose of BNT162b2. A before and after 3rd dose (14 days after) CRP from participants' serum was measured. A Wilcoxon matched paired signed-rank test revealed a significant (P-value <0.05) reduction of inflammatory marker (CRP) after receiving the 3rd vaccine dose. Pre and post 3rd dose quantitative anti-S1-RBD IgG response was measured and compared that revealed a significant boosting effect that clearly correlates with the CRP response. Conclusion: Coverage of vaccines all over the world is still not expected level to control this pandemic. WHO has not recommended the use of a third/booster dose of COVID vaccines. Though our results show some sort of hope for the long COVID in breakthrough events after getting the third dose more study is needed to conclude this issue.