Prior to Delta, studies of breakthrough COVID in vaccinated individuals indicated low viral load. The implication is that breakthrough cases are unlikely to be infectious.  This may not be true with Delta, a bullet point for a Pfizer booster.

Refer to (Rxiv, pdf)  SARS-CoV-2 B.1.617.2 Delta variant emergence and vaccine breakthrough . Quoting from the abstract,

In an analysis of vaccine breakthrough in over 100 healthcare workers across three centres in India, the Delta variant was responsible for greater transmission between HCW as compared to B.1.1.7 or B.1.617.1 18 (mean cluster size 3.2 versus 1.1, p<0.05)….Whilst severe disease in fully vaccinated HCW [health care worker] was rare, breakthrough transmission clusters in hospitals associated with the  Delta variant are concerning and indicate that infection control measures need continue in the post-vaccination era.

Let’s interpret.

• An infection cluster is a bunch of cases in the same place around the same time.
• Although it’s hard to tell who gave COVID to who, a cluster is statistical, not absolute evidence that COVID was passed around the cluster.
• All the workers were vaccinated, though the vaccines used were not quite as stellar as those in common use in the U.S.
• Statistically, vaccinated workers were infected with Delta, and infected other vaccinated workers.
• Certainty (statistical, confidence) grows with time. If you’re a decision maker, you have to pick a point in time.

The concerns of this paper overlap my own. in Delta Strain; the Rough Ride Begins, I wrote,

Yet it allows the possibility that in Arkansas, and even in locales with borderline vaccine uptake, such as LA, community infectivity may overwhelm the protection of the vaccine.

It may be worse. A few more mutations could threaten regions with high vaccination rates. We must rid ourselves of the idea that the COVID threat is stationary. It appears to evolve faster than our thinking.

If you’re in media, you probably want to hear it from an authority. The Institute for Health Metrics and Evaluation, though somewhat tarnished by a poorly performing model, is a source. Search for “Vaccinated People Can Spread the Delta Variant.” Independent has “Warning that fully vaccinated may be spreading Delta variant as cases rise across US.”

(CNBC) WHO urges fully vaccinated people to continue to wear masks as delta Covid variant spreads. Quoting,

“People cannot feel safe just because they had the two doses. They still need to protect themselves,” Dr. Mariangela Simao, WHO assistant director-general for access to medicines and health products, said during a news briefing from the agency’s Geneva headquarters.

“Vaccine alone won’t stop community transmission,” Simao added. “People need to continue to use masks consistently, be in ventilated spaces, hand hygiene … the physical distance, avoid crowding. This still continues to be extremely important, even if you’re vaccinated when you have a community transmission ongoing.”

Two bureaucracies in conflict: WHO versus FDA/CDC. Who are we to believe? Credibility whiplash is the price of public health communicating with the public in a highly managed way. Officials may think of minimizing near-term risk, yet COVID destroys assumptions at a rate too rapid to build credibility. All that’s left is immediate motivation:

• WHO has few doses, but plenty of masks.
• FDA/CDC has plenty of doses, rejected by common ignorance.

With the Delta debacle, WHO-speak  will be a little more durable than FDA/CDC-speak. This has not always been the case. But it may augur yet another crisis in credibility, if we have to go to full-mask lockdown. This is the price of managed communication:

You’re just fine if you do this…It was last week’s advice. Do this instead.

Only one player is sure of what it’s doing: COVID-19. With jabs and feints that belie its brainless, roulette-wheel mutations, it uses managed communication by health authority against the speaker, a grotesque genomic performance.