COVID-19 vaccines help our bodies develop immunity to the virus that causes COVID-19 without us having to get the illness. Multiple Covid-19 vaccines are available worldwide like Covishield, Covaxin, Sputnik V, Pfizer–BioNTech COVID -19 vaccine and Moderna. But do know, why it is essential to take two doses of these vaccines?
Both these doses perform slightly different sub-functions. The first, known as the "prime dose", prepares the human immune system to build antibodies. However, these antibodies aren't long lasting, and they gradually wane with time. This is where the second dose, referred to as the "booster dose", comes in. It boosts the immune system's production of a large number of antibodies, while also stimulating the memory cells, so that the body remembers this infection and continues to create antibodies against it for a long period.
In simpler terms, one dose enables a relatively weaker immune response from the body. Therefore, it requires the extra second dose, which teaches the immune system to produce stronger and longer lasting responses. The second dose also helps to produce more antibodies.
Therefore, without second dose your body will enable relatively weaker immune response which will help our body to fight against Covid-19 to some extent only. But with the second dose your body will able to produce stronger and longer immune response.
Studies exploring the possible benefits of pairing doses from two different COVID-19 vaccines are still ongoing. This concept of mixing vaccines sometimes called a heterologous prime boost-has been beneficial with other infections in the past, and it also helps overcome the issue of lack of availability and supply bottlenecks.
However, WHO's Chief Scientist, Dr Soumya Swaminathan, has insisted that “for now, we stick to using the same vaccines for both doses. At the present time, there isn't enough data for us to recommend this type of interchangeable two-dose schedules… And so, we need to follow what's in that policy advice and for the time being, it is recommended to have the second dose with the same vaccine as you had the first dose.”
