Vaccine effectiveness high against severe Delta-caused COVID-19

A 17-study literature review looking at vaccine effectiveness (VE) during the Delta (B1617.2) variant shows a pooled VE of 90.9% versus hospitalization with a 75.7% and 63.1% VE against symptomatic and asymptomatic infection, respectively.

The results, published yesterday in Eurosurveillance, were based on studies collected until Aug 25. Some studies looked at VE against Delta and Alpha (B117) using sequenced samples, while others looked at VE from time periods where Delta or Alpha was the dominant strain without sequencing samples. Asymptomatic infections (2 studies), symptomatic infections (9), the compound outcome of severe disease and hospitalization (3), and hospitalization alone (4) were looked at, as were VE against Alpha versus Delta (9) and waning immunity (2).

Ten studies looked at VE against infection but didn't demarcate asymptomatic versus symptomatic infections. Pooled VE was 66.9% (95% confidence interval [CI], 58.4% to 73.6%), with one study finding VE for 18- to 34-year-olds was 90%.

VE against mild outcomes was reduced by 10% to 20% when against Delta compared with Alpha but "fully maintained" against severe COVID-19, according to the researchers. Overall, VE against severe disease and hospitalization ranged from 81.5% to 100%, while VE against hospitalization ranged from 75% to 96%.

As for waning immunity, the first study found that Pfizer/BioNTech's vaccine had a 93% VE against infection (symptomatic or asymptomatic) at baseline that declined to 53% after at least 4 months of full vaccination (95% CIs, 85% to 97% and 39% to 65%, respectively). The other study looked at any COVID-19 vaccine given to US frontline workers and found a non-significant change from 85% to 73% VE after at least 5 full months of full vaccination (95% CIs, 68% to 93% and 49% to 86%, respectively).

"Current evidence shows that COVID-19 vaccines licensed in the [European Union] are moderately to highly effective in preventing SARS-CoV-2 infections with the Delta variant, while effectiveness against severe courses of COVID-19 remains high," the researchers conclude.
Oct 14 Eurosurveil study

Delta outbreak in Delhi shows immunity evasion, high transmission

Delhi's COVID-19 outbreak this past spring—the city's fourth since the pandemic began—showed the Delta variant's high transmissibility and higher ability to infect the previously infected, researchers say in a study published yesterday in Science.

The researchers used genomic and epidemiological data taken from Delhi from November 2020 to June 2021. During the 2020 outbreaks, they found that there were no variants of concern, and the Alpha variant was seen occasionally and usually in foreign travelers until January 2021. In March 2021, the Alpha variant surged to comprise about 40% of the cases, but Delta rapidly displaced its dominance in April. A Bayesian model indicated that the Delta variant was 30% to 70% more transmissible than the other COVID-19 lineages seen in Delhi thus far. And, importantly, prior COVID-19 infection provided 50% to 90% of protection against Delta compared with previous lineages.

To see how well the mathematical model held up against reality, the researchers then looked at a cohort recruited by the Council of Scientific and Industrial Research, India, which ranged from 832 to 1,012 people across three time periods. From February to July, the unvaccinated people who were positive for antibodies against COVID-19 went from 42% to 87.5%. Among 91 people who had COVID-19 before the Delta outbreak, 27.5% had increased levels of antibodies, indicating reinfection. Also, regarding breakthrough infections, a single center showed that of 24 cases, Delta was seven times more likely to be the cause.

"The concept of herd immunity is critical in ending outbreaks, but the situation in Delhi shows that infection with previous coronavirus variants will be insufficient for reaching herd immunity against Delta," said co-author Ravi Gupta, PhD, MPH, BMBCh, in a University of Cambridge press release. "The only way of ending or preventing outbreaks of Delta is either by infection with this variant or by using vaccine boosters that raise antibody levels high enough to overcome Delta’s ability to evade neutralisation."
Oct 14 Science study
Oct 14 University of Cambridge press release

Antibiotic prescribing guidelines, diagnostics linked to reduced resistance

Implementing institution-specific guidelines (ISGs) for antimicrobial prescribing and use of diagnostics at a tertiary care hospital was associated with significant declines in antibiotic resistance rates and Clostridioides difficile infections (CDIs), German researchers reported yesterday in PLOS One.

In an interrupted time series analysis, the researchers assessed changes in antibiotic consumption, resistance rates, and CDI incidence over a 9-year period (2012 through 2020) at Leipzig University Hospital. The hospital introduced ISGs in 2014, first in a printed pocket guide and then in an electronic application. The researchers hypothesized that antibiotics prescribed commonly prior to the intervention but not often recommended in the ISGs, such as ciprofloxacin, would be reduced, and that resistance to those antibiotics would decline.

From 2012 to 2020, annual antibiotic consumption per 100 bed days (BD) fell by 14%, from 543 defined daily doses (DDD)/100 BD to 468 DDD/100 BD. The reduction mainly occurred prior to the introduction of the ISGs, most likely because of other antimicrobial stewardship interventions. But fluoroquinolone prescribing fell by 67% during the study period (from 104 DDD/100 BD to 35 DDD/100 BD), a reduction largely associated with introduction of the ISGs and an immediate drop in ciprofloxacin consumption.

The researchers also observed declining resistance rates to most tested antibiotics in all analyzed pathogens except enterococci, where no significant trends were observed. Declines in resistance to broad-spectrum penicillins of up to 25% were observed among Enterobacterales, Staphylococcus, and Pseudomonas. Annual CDI incidence fell by 65%.

"Despite many limitations it seems likely that the reductions in resistance are a result of the decreases and changes in antibiotic consumption," the study authors wrote. "Hence, we recommend the wider use of ISGs for empirical antibiotic therapy because they are relatively easy to implement, reach all clinicians, and have a significant impact on antibiotic prescribing."
Oct 14 PLOS One study

Sequencing suggests new DRC Ebola cases tied to earlier outbreak

Initial genetic sequencing of the Ebola virus isolated in the Democratic Republic of Congo's (DRC's) most recent outbreak suggests a link to the large 2018-2020 outbreak that was centered in North Kivu province, the World Health Organization (WHO) African regional office said yesterday on Twitter.

So far, two cases have been confirmed in the flare-up in Beni, one of the hot spots in the earlier outbreak. Earlier this year, a similar recurrence in Butembo in North Kivu province resulted in 12 cases, all but 1 of them confirmed, and 6 deaths.

Vaccination is under way in the latest outbreak area, and the WHO said its experts are on the ground to help with the response. So far, 220 contacts have been identified and are being monitored.

The WHO has said that sporadic cases after major outbreaks are expected. Survivors can harbor the virus in immune protected parts of the body for longer than 6 months, and animal populations continue to carry the virus, including in the region where the outbreak is underway.
Oct 14 WHO African regional office tweet
Oct 14 CIDRAP News scan "DRC confirmed second Ebola case"

Global flu remains mainly sporadic, led by influenza B

In a global flu update that covers roughly the second half of September, sporadic flu detections were reported in several world regions, including South Africa, which reported a slight rise in both influenza A and B, the WHO said this week. However, flu still remains at lower-than-expected levels in both hemispheres.

Influenza B predominated in North American, Central American, and South Asian detections, while tropical parts of Africa mainly reported influenza A. In Southeast Asia, sporadic influenza A detections were reported from the Philippines.

Elevated respiratory syncytial virus (RSV) activity occurred in some Northern Hemisphere countries, as well as in Caribbean, Central American, and South American countries.

Overall at national flu labs, influenza B made up 68.3% of positive flu detections, and of subtyped influenza A viruses, 84.2% were H3N2. Of the influenza B detections, all belonged to the Victoria lineage.

The WHO included its usual caveats that flu findings could be influenced by COVID-19 related measures and surveillance strategies.
Oct 11 WHO global flu update

Two countries report vaccine-derived polio cases

The Ivory Coast and Nigeria reported new polio cases involving vaccine-derived subtypes, according to the latest weekly update from the Global Polio Eradication Initiative (GPEI).

The Ivory Coast reported one new case of vaccine-derived poliovirus type 2 (cVDPV2) in Guemon province, bringing the number of 2020 cases to 62. In Nigeria, 18 cases of cVDPV2 were reported in 7 provinces: 1 each in Adamwa, Gombe, Katsina, and Tarabe, 2 in Borno, and 6 each in Jigawa and Kano.

The update includes information on a cVDPV2 case in Ukraine, which was reported last week by the European Centre for Disease Prevention and Control. The case involves a 17-month-old girl from Rivne province with acute flaccid paralysis. The current isolate is closely linked to the virus originating in Pakistan. Local authorities and regional and country teams from the World Health Organization (WHO) are conducting investigations to determine the source of the virus.

In other polio news, GPEI reported this week that, following careful review of safety and genetic stability data from mass immunization campaigns conducted with the novel oral polio vaccine type 2 (nOPV2), the WHO's Strategic Advisory Group of Experts on Immunization (SAGE) has endorsed the transition to the next use phase for the vaccine. Rollout of nOPV2 began in March, and approximately 100 million doses have been administered to children in seven countries.

The decision means that more countries will be able to use the vaccine under the WHO's Emergency Use Listing recommendation. Sixteen additional countries have been verified as ready to use nOPV2 by GPEI, and an additional 17 are in the midst of preparations.
Oct 13 GPEI update
Oct 11 GPEI news release
Oct 8 CIDRAP News scan