Antiviral Medications
Both Pfizer and Merck have developed antiviral medications that could help with treatment of COVID-19. Clinical trials for both companies focused on unvaccinated individuals with at least one risk factor for developing severe disease. Pfizer’s drug paxlovid reduces the risk of covid-related hospitalization or death by 89% if the drug is administered within three days of onset of symptoms. Below are some results from the clinical trials:
Of those who were treated within three days of symptom onset, 0.8% (3/389) of patients who received paxlovid were admitted to hospital up to day 28 after randomization, with no deaths. In comparison, 7% (27/385) of patients who received placebo were admitted, with seven deaths (P<0.0001). Similar reductions were seen in people treated within five days of symptom onset, with 1% (6/607) in the paxlovid group admitted up to day 28 (no deaths) and 6.7% (41/612) in the placebo group (10 deaths). Overall, through to day 28, no deaths were reported among patients who received paxlovid, while 10 people (1.6%) in the placebo group died.
Merck’s drug molnupiravir had a 50% relative risk reduction in covid-related hospitalization or death while the absolute risk reduction was 7%. By day 29 after randomization, of those who received the drug as part of the phase III trial, 7.3% (28 of 385) who received the drug and 14.1% (53 of 377) who received the placebo were either hospitalized or had died. Regarding adverse events:
The incidence of adverse events was similar in the groups (35% in the molnupiravir group and 40% in the placebo group). Drug related adverse events were also similar (12% molnupiravir, 11% placebo), although fewer people in the molnupiravir group discontinued treatment because of an adverse event (1.3%) than in the placebo group (3.4%).
Omicron
This preprint article examines reinfection risk with the emergence of Omicron in South Africa. The retrospective analysis includes 2,796,982 individuals who had a positive test result (at least 90 days prior to November 27, 2021). Of the population sample, 35,670 reinfections (0.012%) were identified. Specifically, the authors observed that the number of reinfections during Beta and Delta waves was consistent with the null model of no change in reinfection risk. Omicron, however, illustrated a decrease in primary infections for the model coefficients and an increase in the reinfection hazard coefficient. This population level study provides insightful information and suggests that Omicron may have the ability to evade natural immunity. The authors conclude by stating that there is no epidemiological evidence of immune escape with the Beta or Delta variants.
Furthermore, Omicron may weaken vaccine protection as indicated in this this article by Nature. The first laboratory studies of Omicron and vaccine protection suggested that vaccine protection may be weak but boosters should improve protection. For example, researchers at the Africa Health Research Institute found that the serum (which contains antibodies) from 12 individuals was 40 times less potent against Omicron (Pfizer vaccine). Results have not been peer-reviewed and there is not enough information to determine to what extent the Pfizer vaccine’s ability to protect against Omicron is compromised. This is an evolving situation and more real-time data are needed to provide accurate conclusions.
