First COVID-19 vaccine receives interim recommendation, hydroxychloroquine ineffective for prophylaxis, and more

The FDA Vaccines and Related Biological Products Advisory Committee voted Dec. 10 in favor of the mRNA COVID-19 vaccine developed by Pfizer and BioNTech, leading to an emergency use authorization (EUA) on Dec. 11. On Dec. 12, the CDC's Advisory Committee on Immunization Practices issued an interim recommendation on the vaccine for those ages 16 years and older, with details published Dec. 13 by MMWR.

Earlier on Dec. 10, results from a phase 3 manufacturer-funded trial of the mRNA vaccine were published by the New England Journal of Medicine. Overall, 43,448 people ages 16 years and older received two injections 21 days apart, 21,720 with the vaccine and 21,728 with placebo. Eight cases of COVID-19 occurred at least seven days after the second dose in the vaccine group versus 162 cases in the placebo group, for an overall efficacy of 95%. Ten cases of severe COVID-19 occurred after the first injection, nine in the placebo group and one in the vaccine group. Incidence of serious adverse events was low and was similar between groups.

An accompanying editorial said that while unanswered questions remain regarding safety and distribution, “the remarkable level of safety and efficacy the vaccine has demonstrated thus far make this a problem that we should welcome solving. What appears to be a dramatic success for vaccination holds the promise of saving uncounted lives and giving us a pathway out of what has been a global disaster.”

In other COVID-19 news, a recent U.S. randomized controlled trial found that hydroxychloroquine, which has been proven ineffective for COVID-19 treatment, also appears to be ineffective for postexposure prophylaxis. Between March 31 and Aug. 21, 337 households with 407 participants were randomly assigned to receive 500 mg of hydroxychloroquine daily for three days followed by 200 mg for 11 days, while the control group, made up of 334 households and 422 participants, received similar regimens of vitamin C. All participants were close contacts of a person diagnosed with SARS-CoV-2 infection and had been exposed within 96 hours. The primary outcome was polymerase chain reaction-confirmed incident infection within 14 days in those who tested negative at enrollment.

In the 689 participants who were SARS-CoV-2-negative at baseline, no between-group difference was seen in SARS-CoV-2 acquisition by day 14 (53 events in the treatment group vs. 45 in the placebo group; adjusted hazard ratio, 1.10 [95% CI, 0.73 to 1.66]; P>0.20), although risk for infection was high. Participants in the treatment group were more likely to have adverse events (16.2% vs. 10.9%; P=0.026). “The lack of effect shown in this study builds on other recent data and provides strong evidence against the use of hydroxychloroquine for SARS-CoV-2 [postexposure prophylaxis],” the study authors wrote. The results were published Dec. 8 by Annals of Internal Medicine.

Another study involving households, a systematic review and meta-analysis published Dec. 14 by JAMA Network Open, looked at evidence for household transmission of SARS-CoV-2 and compared it with that of other coronaviruses. The researchers included studies published through Oct. 19 that included original data for estimating household secondary attack rate. The primary outcome was the secondary attack rate for SARS-CoV-2 and other coronaviruses, disaggregated by covariates.

Among 54 included studies with 77,758 participants, the estimated household secondary attack rate for SARS-CoV-2 was 16.6% (95% CI, 14.0% to 19.3%), higher than that for SARS-CoV (7.5%; 95% CI, 4.8% to 10.7%) and MERS-CoV (4.7%; 95% CI, 0.9% to 10.7%). Household secondary attack rates for SARS-CoV-2 were higher with symptomatic versus asymptomatic index cases, for adult contacts versus child contacts, for spouses versus family contacts, and in households with one versus three or more contacts.

The authors noted that the included studies were heterogeneous and that community transmission rates varied across locations, among other limitations. They concluded that based on their results, “households are and will continue to be important venues for transmission, even where community transmission is reduced. Prevention strategies, such as increased mask-wearing at home, improved ventilation, voluntary isolation at external facilities, and targeted antiviral prophylaxis, should be further explored.”

Finally, a brief research report published Dec. 8 by Annals of Internal Medicine looked at persistent symptoms of COVID-19 through day 45 after diagnosis in 669 patients in Geneva, Switzerland, who were not initially hospitalized but were assigned to remote follow-up via ambulatory care. The mean patient age was 42.8 years, 60% were women, 24.6% were health care workers, and 68.8% had no underlying risk factors. Cough and loss of taste or smell were common symptoms early in the disease course. At 30 to 45 days from diagnosis, at least 32% of the 669 patients reported at least one symptom, primarily fatigue, dyspnea, and loss of taste or smell. The researchers concluded that patients with COVID-19 often develop an array of symptoms that appear to evolve over time. “Recognizing the persistence of symptoms could legitimize patients' concerns in an unknown and new disease,” they wrote. “Adequate communication can provide reassurance, reduce anxiety, and potentially optimize recovery.”