At the beginning of the Coronavirus disease (COVID-19) pandemic due to the Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), scientists primarily have focused on diagnostic tests. At the 9th month of the pandemic, discussions are being continued on preventive and therapeutic drugs. Meanwhile, vaccine development strategies like “operation warp speed” gave their early results in developed countries. Nowadays, these vaccines are at the forefront of the world health agenda. Numerous social media posts, conspiracy theories, and some health professional’s statements that raise vaccination hesitancy are the equipment of anti-vaxxers propaganda. On the other hand, declarations like ballyhoo of nationalism with the claims of scientific quacksalvers have intertwined, and that has been led to the loss of trust in the scientific community to the vaccine. We have to admit that this propaganda has affected millions of people in an unwanted direction. Scientific declarations have to rely on researches that have accurate and reliable statistical methods supported with basic biological knowledge. Scientific research results should be disclosed transparently and its methods must have reproducibility to provide replicability. Here, we scrutinize the biological features of the respiratory transmitted and successfully prevented measles virus (MV) and variola virus (smallpox virus) and their vaccines to compare them with the SARS-COV-2 virus and vaccine. Next, we will discuss the statistical details of measuring the effectiveness of an improved vaccine.