Episode 095: Is Herd Immunity Here for COVID?

One of the most commonly used expressions regarding the current COVID pandemic is herd immunity. Policy makers, epidemiologists, and lay people are obsessed with reaching the mythical herd immunity as soon as possible so that we can put this pandemic to bed. It is hoped that the development of a vaccine will get us the herd immunity of 60-80% far quicker than waiting to reach it through natural infections. Not only would that leave behind a lot of devastation and death but would also take maybe as long as 5 years.

However, my guest today says that we may soon be approaching the herd immunity threshold because it really isn't 60-80%. Dr. Gabriela Gomes, a professor of mathematics specializing in infectious modeling, says that her group's modeling leads them to believe we only need to reach between 10-20% infections to actually achieve herd immunity. If she and her group are correct, then many places in the US and world have probably already achieved the herd immunity and can now begin rethinking the need for mitigation procedures.

Dr. Gomes' hypothesis is that her model assumes a variable level of heterogeneity of individuals in their susceptibility to becoming infected with disease. Although her group does not try and figure out what those factors are it simply looks at the current infection and others like malaria and finds that we cannot treat everyone as if they have an equal chance of 'catching' COVID. This is why they find that most models used assuming everyone is equally likely to catch a disease is not robust and fails to catch up with the actual data.

So what does this mean if true? Not only that we will see the virus start to lose its pandemic steam by the end of this year but it will provide us with better strategies of whom to protect and target with vaccines. Perhaps we would shift our focus to vaccinate those who are more at risk of bad outcomes if we now know that a massive outbreak threatening the community is less likely to occur versus a wide scale vaccination program targeting everyone.