An impression in the minds of public after vaccination is a sigh of relief and a hope of freedom from Covid restrictions and end of the pandemic soon. This is a wishful thinking far from being true and needs a complete review of the current efficacy data and the associated concerns
The availability of several vaccines against COVID-19, within one year of the start of the pandemics is a big achievement for the science. We have two vaccines the COVISHIELD from Oxford Astra Zeneca and the indigenous COVAXIN from the Bharat Bio-Tech already available. The SPUTNIK from Russia the first successful vaccine to be produced will also be available by the end of the year. India with a population of 1.2 billion has an enormous challenge at hand to vaccinate its entire population. Smaller populations like Israel have completed this process earlier this month with a negligible case positivity rate of 0.7%. This actually is the best way of achieving herd immunity by vaccinations. Such a gigantic program is rather ambitious in our setting. The availability of vaccine vials in such huge numbers, the set ups for vaccination at the grass root levels in every nook and corner, public motivation to come forward in spite of the Government lifting most of the bars on the age etc are the main issues. In addition, the role of mass vaccination during the pandemic has been criticized because it can lead to new mutants of Corona virus coming out. These could be resistant to vaccines and a capability of very rapid spread.
How early does the immunity to fight the infection come? The answer is not clear because in most vaccine trials second dose was administered within a span of 4 to 12 weeks. The general feeling among the scientists however is that it starts kicking in within two to three weeks, when it starts dipping down. Hence the need of a booster dose. The timing of the 2nd dose for COVISHIELD has been changed from 4 weeks to 12 weeks by Oxford investigators, although our authorities have moved it to 6 weeks. The second dose of COVAXIN is also recommended at 4 to 8 weeks. It is very likely that a booster dose of both vaccines will be required at the end of one year but this is still conjectural. The US vaccines fromG Pfizer and Moderna (m RNA based) have also announced that for those who have received both the doses a third booster dose will be needed and a dose annually thereafter may be required.
A safety signal of particular concern temporally associated with the administration of the adenovirus-based vaccine COVISHIELD has recently come to light after millions of doses being administered worldwide. It is the description of abnormal clotting especially in the veins of the brain and other organs along with a marked lowering of the platelet count. It can lead to symptoms like strokes and vascular events and is potentially fatal. Pfizer and the Johnson and Johnson vaccine has also seen this problem in a few cases.
After initial reviews the manufacturers of these vaccines have confirmed the very small risk of increased clotting associated with them. This risk was however not more than the background risk of vascular events in the general population. The risk benefit ratio is overwhelmingly favouring the vaccine. In a recent study in New England Journal of Medicine 23 such patents have been identified world wide and investigated in detail. The platelet count of these patients was very low and testing for antibodies to platelet factor 4 (PF4) were positive in 96% of these patients. On the basis of these striking findings, scientists have recommended no platelet transfusions in these cases because it can be counterproductive. The administration of anticoagulants like factor X inhibitors (Apixaban and Rivaroxaban) and intravenous immune globulin is the way to go after confirming the diagnosis of this rare complication.
It should also be clearly understood that a successful vaccination does not prevent the person from getting infected and should not lead to complacency in not observing the COVID appropriate behaviour. The infection in these individuals is expected to lead only to milder disease. They can also infect others and those not protected by vaccines can get very severe life-threatening infections because the virus is the same.
Take Home Message:
Everybody more than 18 years of age must be vaccinated against COVID and also motivate vaccine dodgers to get the jab. Vaccination blunts the severity of infection, like the risk of dying and needing ventilatory support. It does not prevent getting the infection or transmitting it to others. Currently available vaccines need booster doses. The complications of blood clotting do occur in a very small percentage of the vaccinated population but can be managed successfully if recognized in time. The benefits of vaccination far outweigh the risks.
Prof Upendra Kaul Founder Director, Gauri Kaul Foundation. A recipient of Padma Shri and Dr B C Roy award