More than 180 countries of the world are badly affected by the Corona crisis. India is also doing two to two hands with him. Even before this, epidemics such as plague, cholera, cholera, polio, flu have endangered humans, but after a time, hard immunity against vaccines, effective medicines and some diseases has kept them under control. The existence of some infectious diseases has ended to a great extent. Diseases of which the strain of the virus does not change. Hard immunity develops towards them. PM Modi is the world's number-1 leader in fighting Corona: Gallup agency survey When 60 to 70% of the people get infected due to an infectious disease, then it has been seen that there is resistance to it. The infection of the coronavirus is also spreading rapidly. Yet even in countries where more people are vulnerable to its infection, 10 to 20% people have not been infected by it. In many places, only three to 5% people have been infected. So it will take time to develop hard immunity towards it. Flu viruses often change their appearance. This is the reason why different vaccines are made every year or the other year for the flu. Corona wreaking havoc in nation, number of infected increasing rapidly The thing to note is that once the vaccine is developed, it becomes easy to make new vaccines. If the coronavirus is stable, if there is no early mutation, then herd immunity can develop in two to three years. If the virus is given a free hand to spread, then it is possible that within a year, so many people will be infected and then resistance will also develop in the people, but it will be a risky step. Because a lot of people will die in it. If the virus format changes then it can increase the problem because it is a new virus right now. No country has more than three-four months of experience. It will have to be monitored for six months. Mann ki Baat: PM said on corona, says, 'everyone is a soldier'