More Breakthrough Infections Reported, Pfizer-BioNTech Vaccine Receives Full Approval


The Centers for Disease Control and Prevention (CDC) released data this week that showed greater breakthrough infections in a large study mainly compiled before the emergence of Delta as the predominant variant in the US.

us infections

A CDC report this week showed that 25% of people infected with SARS-CoV-2 in Los Angeles County, Ca., from May 1, 2021 to July 25, 2021 were fully vaccinated. This shows a substantial amount of breakthrough infections prior to the Delta variant as the predominant strain in the United States.

“…Among 43,127 SARS-CoV-2 infections in residents of Los Angeles County, California, 10,895 (25.3%) were in fully vaccinated persons, 1,431 (3.3%) were in partially vaccinated persons, and 30,801 (71.4%) were in unvaccinated persons.”

The Los Angeles County Department of Public Health (LACDPH) wanted to study post-vaccination infections and used COVID-19 surveillance and California Immunization Registry 2 (CAIR2) data to describe age-adjusted infection and hospitalization rates during the aforementioned timeframe by vaccination status.

The report showed people who were fully vaccinated fared much better in terms of avoiding serious infection. “Much lower percentages of fully vaccinated persons infected with SARS-CoV-2 were hospitalized (3.2%), were admitted to an intensive care unit (0.5%), and required mechanical ventilation (0.2%) compared with partially vaccinated persons (6.2%, 1.0%, and 0.3%, respectively) and unvaccinated persons (7.6%, 1.5%, and 0.5%, respectively) (p<0.001 for all comparisons),” the CDC reported. “On July 25, the SARS-CoV-2 infection rate among unvaccinated persons was 4.9 times and the hospitalization rate was 29.2 times the rates among fully vaccinated persons.”

During this time period, the vaccination rates did increase substantially. The percentage of fully vaccinated residents in LA County was at 27% on May 1 and increased to 51% on July 25.

First There was Alpha, Now Delta

A good portion of this report was captured when the Alpha variant was considered the dominant strain in the United States.

It is becoming clear, however, the Delta variant is far more infectious than Alpha—even for the fully vaccinated. In a CDC Morbidity and Mortality Report released a few weeks ago, it was found that vaccinated people carry as much viral load in their noses as the unvaccinated.

In fact, the variant decimated India in the spring and worked its way west.

The overall evolution of Delta as the predominant strain in the US has been staggering. Contagion Editor-in-Chief Jason Gallagher, PharmD, FCCP, FIDP, FIDSA, BCPS, pointed this out in his August Editor’s Letter.

“At the end of May, the Delta variant was responsible for 3.1% of infections, while the Alpha variant was 69.1%; at the midpoint of July, Delta had caused 83.2% of infections and Alpha was 8.3%,” Gallagher wrote. “That is an enormous swing in under 2 months.”

In early June, the CDC classified the variant as “Emerging,” and that 6% of American COVID-19 cases were from Delta.

“This variant is now identified to be more transmissible than even other hyper transmissible variants like the one from the UK,” CDC Director Rochelle Walensky, MD, said in an interview at that time. "We also know that while our vaccines do work against it, they don’t have as much buffer in terms of protection as some of the other wild type strains. So the concern is not just the more transmissibility—and we have seen more virus in the UK where this variant has also emerged—if we have this other variant circulating here it may lead to a more virulent variant such that our vaccines wouldn’t be able to work.”

Vaccine Updates

This week saw some major movements in terms of the 3 COVID-19 vaccines that have Emergency Use Authorizations (EUA) in the US.

With studies reporting more breakthrough infections and waning immunity, US public health officials have been prompted to move on approvals on vaccines and booster doses. For example, the Food and Drug Administration (FDA) gave the Pfizer-BioNTech vaccine, BNT162b2 (Comirnaty), a full approval on Monday. This has opened the door to more mandates, and companies, state and local governments have already announced vaccine mandates in the wake of the approval.

In addition, one report said the federal government is planning to shorten the period of time between the second dose of the COVID-19 vaccine and the booster dose from the previously discussed 8 months to 6 months.

On Wednesday, there was a flurry of news for all 3 vaccines. Pfizer-BioNTech announced they had initiated a rolling submission for their COVID-19 vaccine to seek an FDA supplemental Biologics License Application (sBLA) that would allow for marketing and prescribing of a third booster dose of the vaccine for fully vaccinated individuals aged 16 years and older.

Moderna announced it has submitted its formal BLA with the FDA for its COVID-19 vaccine, mRNA-1273, and Johnson & Johnson announced that same day positive data supporting a booster dose of its COVID-19 vaccine, Ad26.COV2.S.

The speed that the Delta variant has taken hold has made public health officials pivot and address both full approvals and boosters. Whereas, just a few weeks ago, it seemed we had turned a corner for the better, this strain of COVID-19 has made us rethink our collective health approach to the virus.

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