Thread by @MonicaGandhi9

Wanted to explain concept of CONTROL vs ELIMINATION (& eradication) with an infectious diseases, why getting immunity up in a population can get us to control, & why living with a controlled infectious diseases is very manageable (and no longer problem of the public just ID MDs)

Even though we tried to control COVID with other strategies (masks, distancing, ventilation, testing, contact tracing), true control of a pathogen achieved when a significant proportion of the population becomes immune. Never this degree of testing done for a pathogen before.

In 1918 influenza pandemic, masks, distancing, closures employed but there was no vaccine developed for influenza until 1942. So, instead the pandemic came to an end through terrible loss of human life, 50 maybe up to 100 million dead, 5% of world's population.

But since vaccines developed, infectious diseases could be controlled. 4 concepts in ID epidemiology- control vs elimination vs eradication vs extinction. Control takes vaccines, medications, contact isolation or other public health interventions
pedaids.org/2015/02/18/hiv…

to bring infections down to manageable level and MOST importantly, ensure that few become sick or die from the disease. That is where we are getting in US, UK, Canada and other countries with mass vaccination: numbers of hospitalizations/deaths decreasing massively. Infections

- at least asymptomatic infections or having virus in nose- were tracked to prevent spread to others, but weren't a sign of infirmity as by definition, they were asymptomatic. So, continuing to screen those who are asymptomatic after vaccination given unlikely to spread is not

good use of public health resources (and not endorsed by CDC, I try to explain here). So, is the virus getting to control in countries with access to vaccines and mass vaccination? Yes, it is by traditional ID definitions. Okay so what about ELIMINATION

https://twitter.com/MonicaGandhi9/status/1395572466949365761

ELIMINATION means stopping the transmission of a disease in a specific geographic area or country (not worldwide). Dr. Fauci said to WaPo on May 22 when cases dipped below 30K that we want to get to "level that isn’t a public health hazard
"washingtonpost.com/health/coronav…

that doesn’t disrupt society". The reason we are aiming for control but not elimination is that some of the public health restrictions we have employed in the name of elimination (closing schools, businesses, etc.) are extremely disruptive to society & enact collateral damage. So

what does control look like? Control looks like measles in the US which is not a problem of the public but a problem of ID MDs and public health practitioners. Outbreaks occur in pockets of unvaccinated people or when unvax'd traveler brings from abroad.
cdc.gov/measles/cases-…

And of course we do not test routinely for measles so are only aware of a measles case when someone presents for medical care with typical symptoms. That is where we will get with COVID - will test people with symptoms & identify outbreaks as population immunity rises. In Israel

there are 26 people with COVID in the hospital (out of 729 cases, we won't know about asymptomatic cases in future when not testing like this with control) & near zero deaths. So, this is a small "outbreak" in a place still vaccinating. US and UK still vaccinating too. Between

immunity from natural infection + immunity from vaccination, community immunity gets so high that there will only be small outbreaks that will be well-managed with medication (which is why developing outpatient antivirals so important) and ring vaccination. Places opening in US

at less than 70% 1st dose vax rate and cases not surging because combination of natural immunity + vax. Places like San Francisco with such high levels of vaccination (plus some natural immunity) exhibiting control. Control is our goal with COVID; doubt elimination possible &

restrictions damaging. And eradication - which means worldwide elimination- has only been achieved with smallpox (declared eradicated by the WHO in 1980. To be made "extinct", remaining vials of live variola (smallpox) virus would have to be destroyed
passporthealthusa.com/2019/10/why-do…

Who will decide on control vs elimination for a country? Likely political leaders not CDC or NIH or their equivalent Elimination would be nice but may be too high a price on society; Control allows outbreaks to be managed by MDs (which is why antivirals & ring vax important)