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Expert predicts herd immunity by May, but certain roadblocks could prevent it

Dr. Joe Gerald explains that, while Arizona approaches herd immunity, the community is not out of the woods.

PHOENIX — Editor's note: The video above is from a VERIFY segment that aired on 12 News in Dec. 2020. 

University of Arizona professor and researcher Dr. Joe Gerald released a new COVID-19 update for the state that included an exciting prediction about herd immunity. 

In the report, Gerald said that as case positivity continues to decline and the number of vaccine doses continues to rise, Arizona could see herd immunity by late April or early May. 

While that is a positive outlook for the coming months, there are some things to keep in mind. 

Herd immunity is assumed to kick in when 58% of the population have been vaccinated or have recently recovered

In his report, Gerald explains that herd immunity is based on several factors including "vaccine efficacy, viral transmissible and natural immunity."

Gerald estimated that about 40% of the state's population has been infected with and recovered from the virus, which means that 30% of the adult population will need to be vaccinated to reach the immunity milestone. 

There are some details to keep in mind

Gerald explained that while the progress looks encouraging, there are a few things that people need to keep in mind. 

First off, the numbers above are only possible if the original variant of COVID-19 remains the dominant strain. If a new variant takes over as the most transmissible, more vaccinated people will need to be reported before researchers can positively claim herd immunity. 

So far, Arizona has seen two mutated variants of the virus including the strain first identified in the UK and the one first identified in Brazil.

Also, the current percentage needed for herd immunity is only right under the assumption that children are "dead-enders". 

"Meaning they don't transmit much to adults or peers," said Dr. Gerald. "In that case, delaying their vaccination until it is FDA-approved will not fundamentally impact how many adults need to be vaccinated."

Finally, this theory assumes that natural immunity can last long enough for more Arizonans to be fully vaccinated. 

Just because herd immunity is achieved does not mean you can't still catch the virus

According to Gerald, herd immunity only means that "the virus is no longer capable of self-sustained transmission in the wider community."

Smaller populations can still sustain outbreaks if they have not built the correct levels of natural and vaccine-based immunity.

"There will still be meaningful risk until COVID-19 is brought to heal everywhere," Gerald said. 

Until the country as a whole reaches a sustainable level of immunity, everyone should continue proper mitigation tactics. 

To read the full report, click here. 

For full coverage on COVID-19 and vaccine distribution, subscribe to the 12 News YouTube channel.