Explained: Is it time to discuss vaccine booster shots in India?

Data released recently by the Brihanmumbai Municipal Corporation BMC suggested that out of the 54 percent breakthrough cases of Covid19 registered between February 1 and September 24 351 percent were vaccinated with at least one dose and 198 percent had received both doses of the vaccineThe vaccine has largely diluted the effect of the virus and the infection is either not serious or very mild in the breakthrough cases registered the BMC further saidThese reports came at the same time as updates of health workers in Mumbairsquos hospitals getting a booster shot due to a reported decline in the amount of antibodies present in the body months after taking the second dose of Covid19 vaccineAs the discussion around vaccine effectiveness and booster shots intensifies there is a risk of misinformation and unnecessary panic spreading among the publicMidday online reached out to two citybased experts Dr Rahul Pandit director for critical care Fortis Hospitals and a member of Maharashtrarsquos Covid Task Force and Dr Pruthu Narendra Dhekane consultant and infectious diseases specialist at Fortis Hospital They explain the meaning of efficacy of vaccine double dose in simpler terms and offer clarity over whether Indians require booster shots anytime soonWhat do we mean when we talk about the efficacy of double dose of Covid19 vaccinesPandit The efficacy of a double dose of the vaccine is measured 15 days after the second dose has been administered and when the person has developed a full antibody response Efficacy is looked at in the form of the chances of reducing mortality as a result of vaccination This is the primary way in which the efficacy is actually measured The secondary way of efficacy measurement is the infective rate ie whether it will bring down the actual number of infections But remember thats not the primary reason why the vaccines are actually produced and administeredOn September 9 Indian Medical Council of Research ICMR Director General Dr Balram Bhargava stated that the effectiveness of Covid19 vaccine in preventing mortality after a single dose is 966 percent while it is 975 percent after the second dose Does this also mean there is lesser transmission or infection risk among the publicDhekane After receiving two doses of the vaccine the chances of a person catching COVID19 disease are relatively the same but the chances of a person developing symptomatic illness reduce significantly This means a person may contract the COVID19 virus but it might not cause symptoms If symptoms are generated they may be mild or moderate They wont be severe at least in 969737 of cases according to ICMRThat doesnt mean there is lesser transmission However if you are vaccinated with two doses and after that you do get infected with COVID19 even if you are asymptomatic or mildly symptomatic the chance of further transmitting the virus to other people reduces The duration of illness or symptoms is also reduced Hence the cases of transmission of virus also decrease so therersquos lesser risk in the general public if everyone is vaccinated with the primary series of vaccines two dosesRecent studies from US UK and Israel suggest that vaccine efficacy declines within a period of three to four months Is this a cause for concern in India given the Delta variant casesPandit As per the recent data from UK and US which talks about a decline in efficacy after three to four months of vaccination we know that antibodies do get lower after few months however it does not indicate the decline in the level of immunity in a person Immunity mainly depends on the T cells and I think that is not very easily measured by many of us We know that the second wave of COVID was predominantly due to the Delta variant in India therefore as long as we donrsquot have any other new variant of concern that will be more infectious than the Delta variant it wont be a big concern for usDhekane The vaccine efficacy declining over 46 months is more so of the bodys Bcellmediated antibody levels which decrease This results in more susceptibility of an individual getting COVID after 36 months or maybe after a year where we need more data or studies to show that this is the scenario The Delta variant isnt a concern because most vaccines available are covering itHow do you assess the efficacy period of Covishield and CovaxinDhekane It is challenging to assess the efficacy period of any vaccine Measurement of antibodies is not an appropriate way to measure the efficacy period of the vaccine definitely not of the COVID vaccine because it is the newest and the youngest vaccine on the block Maybe we require a year or every six months to generate more immune responses As far as Covidshield and Covaxin are concerned it will have a Tcell and Bcellmediated reply The antibody levels are Bcellmediated which will decrease with time but that does not mean you will not stay protectedHow will a booster shot helpPandit The booster dose will actually improve the antibody levels and thereby it will actually help in restoring the immune responseDhekane In the absence of sufficient safety and efficacy data it is difficult to say if a booster shot will help or not and there are chances of an excessive immune response leading to side effects in the event of more exposure to COVID antigensThere are reports of health workers being administered a third booster shot in Mumbai hospitals due to a reported decline in antibodies among the health workers and LH Hiranandani Hospital has even written to the state government for a third booster shot Does Mumbai need booster shots as of nowPandit No Let the population get vaccinated first Let all Indians have at least one dose of the vaccine Let more than 6070 percent of the people get their vaccines Then I think the case for a booster dose can be madeDhekane I dont think Mumbai needs to be separated from the rest of the country when it comes to booster shots The dynamics are different because of population density Still its better to wait for more concrete data on the safety and efficacy of the third dose of the vaccine to come into the pictureThe majority of the people especially healthcare workers are concerned because they received their vaccine in January or February this year and it has been close to nine months Some are concerned if their antibody levels are declining and some are excited to check their antibodies monthly What are the dos and donrsquots of booster shots and at what stage is it generally administeredPandit There is no case of a booster dose being discussed right now hence we should wait for some more data and research to come to light before taking any further actionAccording to government data out of the 9079 crore people vaccinated as of October 3 only 2481 crore that is 18 percent of the total population of the country have been administered the second dose of the vaccine Can we afford booster shots at the moment considering the gap in the number of people yet to be fully vaccinatedDhekane Rather than going in for a third shot its essential to close the gap between people who are not immunised or have received just one dose of vaccine The earlier we get this done the lesser the chances of having another outbreak or other waveAny misconceptions or misinformation around double doses and booster shots that you would like to bustPandit Two doses are necessary with the current available vaccines only When Johnson amp Johnson or ZyCovD vaccines are available it will be a one dose vaccine or a three dose vaccine So whichever vaccine you are administered with make sure that you complete the regime of that particular vaccineDhekane Well theoretically double dose in vaccinology and booster shots mean different things A double dose is recommended to give twice the strength of the regular dose of vaccine Booster shot means that once you have completed an initial series of vaccines called the primary series of vaccines you require the same amount of vaccine within a required time which will keep your protective level of a particular disease at an optimum We recommend annual doses of influenza vaccines These are not booster doses These are given to combat the newer strains and variants which come up every year for influenza Dont confuse double booster and yearly doses of vaccinesAlso Read Does Coronavirus catch young hearts Doctors look for answer