Mix and match?
Is a combination of vaccines more effective against COVID’s variants? The jury’s out
The search is on in India for the most effective vaccine or a combination of vaccines against COVID-19 and any of its dangerous, Delta or Delta Plus, variants. The latest study by the Indian Council of Medical Research (ICMR) claims a combination of Covishield and Covaxin — the only two vaccines most used for vaccinations in India — may yield an effective result. The study was conducted on some patients in Uttar Pradesh who were erroneously given the second dose of a vaccine different from the first one. The study sample is too small to come to any confirmed conclusion and it is not possible to talk in percentages either. However, it may shortly lead to a bigger study by the Christian Medical College, Vellore, and that should come up with reliable readings. The fact that there was no adverse impact of the UP error does not necessarily mean the combination is effective. The emphasis, till a formidable result is out, has to be on the fast-paced vaccination of the population. As of date, two doses of the same vaccine, whether Covishield or Covaxin, are found effective to minimise the chances of hospitalisation and death in the case of an infection. How much more can a combination dose minimise the infection is yet to be scientifically known. A question of bigger concern for the scientific community should perhaps be whether the effectiveness of the double dose of a vaccine reduces over a period of time and, if so, how to boost the immunity levels.
Does a person who took the jabs in January or February enjoy the same level of protection today as six months ago? The supplementary question should then be whether a vaccine’s reduced effectiveness over time can handle a stronger variation of the Coronavirus? If not, does the fully vaccinated person require a booster shot to maintain the original effective levels and at what point of time can a decision on a booster dose be made? The COVID-19 task force of the Union Health Ministry would obviously be thinking along these lines and since there is a segment of population that has taken both jabs six months ago, there should be a process of determining their effectiveness levels and zero in on booster options. Studies abroad are suggesting that antibody levels triggered by most COVID-19 vaccines are dropping. However, they do not yet know if the dropping levels mean lesser protection against the virus. There is advanced research being undertaken across the world to determine the precise level of antibodies or an immunity marker at which a vaccine’s effectiveness can be said to be waning. In scientific parlance, it is known as the correlation of protection and when the threshold is reached, it will indicate that a booster dose may be required. Israel’s Ministry for Health has claimed that vaccine protection against infection has dropped within a period of six to seven months. We have to wait for the ICMR’s studies.
Source: The Pioneer
