Thread by @celinegounder

1/ CDC has shortened the recommended isolation period for COVID from 10 days to 5 days if symptom-free at 5 days
& recommends that people then wear a mask for 5 more days.

cdc.gov/media/releases…

Is this good advice?

2/ We ISOLATE people who HAVE COVID.

We QUARANTINE people who’ve been EXPOSED TO COVID.

3/ CDC recommendations are reasonable IF PAIRED with rapid antigen testing to come out of isolation.

Why? People are infectious for a wide range of time. Some for a couple days. Others, for over a week.

4/ An average number of days since diagnosis
or presence/absence of symptoms
are not great measures of infectiousness.

We need objective measures of infectiousness.

Rapid antigen tests provide a measure of infectiousness.

5/ Here’s a study of viral shedding over time from early in the pandemic.

Many people were no longer infectious by 7 days after symptom onset.

But many were still infectious out to 14+ days.

nature.com/articles/s4159…

6/ Here’s a more recent study of viral shedding over time. It spikes up at first during the initial phase of infection when the virus is replicating and then goes down once the immune system kicks in.

nejm.org/doi/full/10.10…

7/ Note that Fig 1G compares time to viral clearance among vaccinated (mean 5.5 days, 95% CI 4.6-6.5 days) versus unvaccinated (mean 7.5 days, 95% CI 6.8-8.2 days).

Vaccinated persons clear the virus faster.

8/ Note that this study includes Alpha and Delta, but was pre-Omicron.

We don’t yet have comparable Omicron data.

9/ CDC policy is being driven by scarcity.

Early in the pandemic, people were told not to get medical-grade masks.

Not because masks didn't work to protect against COVID. They do.

But because masks for healthcare workers were in short supply.

10/ Now CDC's isolation policy is being driven by a scarcity of rapid antigen tests.

We need to make rapid tests widely available and accessible for free.

We should build our isolation & quarantine policies around rapid testing.

11/ And a strong foundation of rapid testing would enable prompt, equitable distribution of new antiviral treatments for COVID (e.g. Paxlovid).