The Memorial Day holiday will be a true, but not absolute, test of herd immunity.

Many people have talked about Memorial Day being the 1st “normal” holiday since the COVID epidemic. Clearly restrictions have been eased and group activities were much more coordinated than we have previously seen. We will all be looking to see whether there will be an infection spike after major events that occurred during the Memorial Day holiday, simply due to individuals congregating on beaches and swimming pools.

Despite hoping to get insights into whether the pandemic spread of COVID-19 has been blunted, there are some unique aspects to the activities on Memorial Day weekend that may keep us from truly understanding if we have finally moved beyond the COVID-19 pandemic.

The 2021 Indy 500 crowd

1) Most of the activities that were large group encounters were conducted out of doors. For example, the Indianapolis 500, despite having large numbers of individuals in a crowded space, was mainly outdoors where UV light, breezes, and other factors made it much less likely that COVID-19 would be transmitted. Therefore, not seeing surges in infections after these events may not tell us much about the potential for COVID-19 transmission in the future.

San Diego Beaches this Memorial Day

2) Many individuals who are not vaccinated seemed to be taking precautions. From local discussions, many unvaccinated individuals were avoiding group events. Others were wearing masks and using other types of respiratory precautions. This may keep infections from spreading even among those who are not vaccinated.

Daytona Beach last weekend.

3) Vaccination rates vary significantly across the country making analysis difficult. While it may be that we will be able to correlate transmission events with background vaccination rates within communities, travel may make this difficult. In fact, there may be evidence of transmission in urban areas where vaccination rates are the highest due to visitors from areas with lesser rates of vaccination.

4) Vaccination rates have yet to rise in younger people below the age of 18 because the vaccines have only recently been approved for these populations. Youth athletic events and other school activities may still be a problem among young people until higher rates of vaccination are achieved.

Therefore, let’s all hope there will be no increases in COVID-19 infection rates after this weekend, but remember that this weekend’s results may not predict what might happen with this infection in the fall or winter.

Published by jbakerjrblog

Immunologist, former Army MD, former head of allergy and clinical immunology at University of Michigan, vaccine developer and opinionated guy.

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