OMICRON-ADAPTED BOOSTERS Previous COVID-19 Situation Reports have outlined the United States’ and other countries’ decisions to prioritize SARS-CoV-2 vaccines adapted to newer viral variants for future booster campaigns. New variants are differentiated from the original strain of the virus targeted by initial vaccines, showing significant mutations in portions of the spike protein. This differentiation reduces the effectiveness of current vaccines, as well as natural immunity gained through previous infection, and has contributed to surges in COVID-19 cases in many countries.
For many months, public health experts and scientists have discussed the promise of new vaccines, targeted for specific variants. Both Pfizer-BioNTech and Moderna are primed to offer versions of their COVID-19 vaccines specifically tailored to target various sublineages of the globally predominant Omicron variant. The UK became the first country to approve a bivalent COVID-19 vaccine for use as a booster among adults on August 15, authorizing the use of Moderna’s “Spikevax bivalent Original/Omicron,” which targets both the original SARS-CoV-2 strain and the Omicron BA.1 variant. Canada this week announced it has secured 12 million doses of an Omicron-adapted vaccine from Moderna, and the government is currently reviewing bivalent vaccine submissions from both Moderna and Pfizer-BioNTech, with decisions expected in about 2 weeks. Vaccines under review are targeting the original virus and earlier Omicron lineages.
In the US, the government has agreed to purchase 66 million doses of Omicron-adapted vaccines from Moderna and 105 million from Pfizer-BioNTech, but those vaccines are expected to target the original virus and the BA.4 and BA.5 subvariants instead of BA.1. Pfizer and BioNTech this week requested emergency use authorization (EUA) from the US FDA for the companies’ Omicron BA.4/BA.5-adapted vaccine for individuals aged 12 years or older, despite the lack of new clinical data on the shot. In the same announcement, the companies said a trial investigating the safety, tolerability, and immunogenicity of the Omicron BA.4/BA.5-adapted bivalent vaccine is expected to start this month. The companies have provided the FDA with preclinical and manufacturing data on the vaccine, but they have not yet made that information public. Despite the later start researching and making a US supply, the companies say the mRNA platform is well-suited for quick adaptations and federal health officials remain steadfast that the newer bivalent vaccines will be available by mid-September.
Current projections suggest that any person aged 12 or older who has completed a primary COVID-19 vaccination series will be eligible to receive these booster doses when they become available. This projection could change as data come in and are considered, and eligibility could differ among any authorized vaccine boosters. Scientists agree that these new booster doses likely will help improve the nation’s immune protection, but some question how well they will work given that oftentimes, the version of a virus to which an individual has an initial immune response can impact responses to future variants and vaccines. Additionally, many public health experts are worried that the prevailing “COVID is over” sentiment in many countries will negatively impact uptake of vaccine boosters.
NOVAVAX VACCINE EUA On August 19, the US FDA expanded its emergency use authorization (EUA) of Novavax’s protein-based COVID-19 vaccine to include adolescents. The FDA initially authorized the 2-dose primary series vaccine for adults in July, demonstrating 90% efficacy, and the shots will now be available for individuals aged 12 to 17, among whom it showed 80% clinical efficacy. The 2 doses are given 3 weeks apart. The Novavax vaccine uses a more traditional, protein-based technology that teaches the immune system to recognize small, modified pieces of the coronavirus spike protein. This older technology is also used in vaccines for hepatitis B, HPV, and pertussis. The Novavax vaccine also contains the Matrix-M adjuvant, which helps to induce a broader immune response. In July, the company announced that the vaccine shows “broad” immune response to circulating variants, including Omicron BA.4 and BA.5. However, Novavax is also working on an updated version of the vaccine that specifically targets the Omicron variant and subvariants. The company intends to file for authorization for a bivalent vaccine later this year.
PAXLOVID REBOUND The US FDA has requested that Pfizer conduct a study examining an extended course of its antiviral Paxlovid among individuals who experience a rebound of COVID-19 after taking an initial 5-day course. The FDA wants to know if a second 5-day course of the antiviral would help prevent disease rebound, and has requested that Pfizer produce initial results of such a trial by September 30, 2023. While Pfizer claims that disease rebound following Paxlovid treatment remains rare, several high-profile cases have prompted the FDA’s request for further study into the phenomenon.
INCUBATION PERIOD According to a study published August 22 in JAMA Network Open, the incubation period of COVID-19 has decreased gradually as SARS-CoV-2 has continuously evolved and mutated, producing variants with different enhanced transmission and virulence. The incubation period is the interval between exposure and development of symptoms and is an important epidemiologic indicator for understanding transmission. Based on the authors’ meta-analysis, the initial “wild type” strain first detected in Wuhan, China, in 2019 had an incubation period of approximately 5.2 days. Later in 2020, the Alpha variant that quickly became dominant in the UK had an incubation period of about 5 days. The Beta variant was identified shortly after and showed a shortened incubation period of 4.5 days, followed by the Delta variant with 4.41 days. The incubation period for Omicron infection is currently 3.42 days. While a decrease in incubation period often is associated with more severe disease, the decrease with COVID-19 means it makes it much more difficult to control transmission, because the faster someone becomes contagious, the faster an outbreak spreads. Knowledge of this key epidemiological parameter is helpful not only in reducing local transmission but also in understanding presymptomatic transmission.
HOME ANTIBODY TESTS The advent of home antigen tests for SARS-CoV-2 were an important step in helping people gain real-time knowledge of their infection status so they could isolate at home and hopefully stop chains of transmission. Now scientists are working to develop at-home antibody tests to help people determine their level of protection from infection and whether they might need an additional vaccine booster. A new study published this week in Cell Reports Methods describes a finger-prick test to detect neutralizing antibodies against SARS-CoV-2. If the test holds up to large-scale testing, it could provide an inexpensive way for people to learn how well-protected they are against the virus, although they might still be susceptible to newer viral variants capable of evading certain immune system responses.
UK COVID-19 INQUIRY Officially launched in July, the UK COVID-19 Inquiry is an independent panel established to examine the UK’s response to and impact of the COVID-19 pandemic and provide lessons for future pandemic preparedness and responses. Now, a coalition of 9 health and development nongovernmental organizations (NGOs) are calling for the inquiry to expand beyond its focus on the domestic response to also consider in what ways the UK government’s response contributed to growing global inequities during the pandemic. The NGOs—including Oxfam GB, Save the Children UK, Médecins Sans Frontières UK, and Health Poverty Action—sent a letter on August 22 requesting an expansion of the investigation. Another signatory, RESULTS UK, released a report August 16 outlining and assessing various UK government actions in response to the pandemic and providing recommendations for the UK government, including the UK COVID-19 Inquiry be broadened. Inquiry representatives have not yet indicated whether they will expand their examination.
In related news, several US Republican lawmakers have vowed to investigate the role certain individuals played in the US COVID-19 pandemic response if they gain control of the House of Representatives or Senate next year. One figure is Chief Medical Advisor to the White House and NIAID Director Dr. Anthony Fauci, who formally announced his retirement from public service this week.
IRAN In an investigation, the Washington Post outlines how members of Iran’s government and the domestic pharmaceutical company Barkat pushed through the approval of a yet-unproven COVID-19 vaccine during the country’s worst SARS-CoV-2 surge. The company failed to deliver an agreed upon 50 million doses, and most Iranians were vaccinated with a Chinese-produced vaccine. Nevertheless, Barkat’s profits soared, and the company appears to have compensated government officials who sat on its board and pushed the vaccine’s approval.