Polk

“There’s this attitude that public health measures are getting in the way of opening up the country. It’s exactly the opposite…the public health measures are the pathway to opening the country. That’s the point that gets lost.” — Dr. Anthony Fauci.

A former university colleague was known for asking challenging questions in his classroom. The appropriate answer often required the student to qualify their response by saying, “It all depends,” and then identify the conditions that make their answer true.

“When will the pandemic end?” The short answer is, “It all depends.” The longer answer is the subject of this column.

Person-to-person transmission of the SARS-CoV-2 virus, and therefore the incidence rate of COVID-19 infections, depends on these conditions:

• The proportion of the population adhering to behaviors that reduce transmission, including masks, physical distancing and personal hygiene such as handwashing.

• The proportion of the population already infected who are therefore immune, currently 25-40%.

• The proportion of the population who are immunized, currently 21%.

Achieving herd immunity is the goal of vaccination. Herd immunity means the virus has too few new people to readily infect so the pandemic dies out. The proportion of the immune population required to achieve herd immunity is 70-85%. The sum of current U.S. immunity (above) is short of 70%. Rapid immunization of the remaining vulnerable population is why we have been waiting for our age groups to be summoned to Cloverleaf Hall.

Scientists at Public Health Informatics, Computational and Operations Research (PHICOR) have modeled these complex relationships.

Graph A illustrates that under conditions at the time of the analysis (Feb. 16), including 1.7 million immunizations per day, the rise in the proportion of the US populations with infection plus vaccine induced immunity (top dotted line) will reach 70% in July. If only vaccine-induced immunity is considered (lower dotted line) then 70% will not be reached until November.

Graph B illustrates increasing immunization to 3 million per day (beginning Feb. 16), herd immunity will occur in May, two months earlier. There are also 10,000 fewer predicted deaths.

Additional scenarios, including the effects of loosening social restrictions and the impact of variants can be viewed online (www.nytimes.com/2021/03/04/learning/whats-going-on-in-this-graph-march-10-2021.html). The strength of these models is that it is easier to understand the reasons why we have altered our lives for the past year, and the goal that we all have — to return to a semblance of normality.

There are additional issues that need to be considered as our society tries to achieve herd immunity:

• Vaccine hesitancy. The U.S. is currently vaccinating an average of 2 million persons per day. Some say 3-4 million doses per day are achievable. A Pugh survey reported March 5 found that 30% remain reluctant or opposed to vaccination. This will delay achieving herd immunity.

• What’s normal? “How long to get back to normal?” depends on how you define normal. Dr. Fauci recently said, “If normality means exactly the way things were before we had this happen to us, I can’t predict that.” President Biden has said, “we’ll be approaching normalcy by the end of this year.”

Few scientists believe the SARS-CoV-2 virus will be eradicated. Instead it will likely become endemic, perhaps like annual influenza. The unvaccinated will continue to be vulnerable to infection. There will be a new normal.

Is everyone on board? Although new infections are decreasing, a return to “normal” social behavior too early is concerning. Governors of Mississippi and Texas reversed mask mandates for residents on March 2, decisions that were widely criticized by public health officials. On March 5, the federal Center for Disease Control and Prevention (CDC) reported new data confirming the importance of masking.

• Variants. Scientists are monitoring COVID-19 “variants of concern” that have lower sensitivity to current vaccines. Vaccinations will reduce variants that may threaten us all. Updated vaccines that target variants may become part of routine vaccinations for SARS-CoV-2 in the future.

• The bubble. This review has focused on the U.S., but we don’t live in a bubble. One estimate is that it could take 7 years to achieve herd immunity for the rest of the world.

• The bottom line. “When will things return to normal?” It all depends…on us.