COVID-19 Situation Report
Editor: Alyson Browett, MPH

Contributors: Clint Haines, MS; Natasha Kaushal, MSPH; Amanda Kobokovich, MPH; Christina Potter, MSPH; Matthew Shearer, MPH; Marc Trotochaud, MSPH; and, Rachel A. Vahey, MHS.
EPI UPDATE The WHO COVID-19 Dashboard reports 270.8 million cumulative cases and 5.32 million deaths worldwide as of December 15. Global weekly incidence increased for the eighth consecutive week, up 0.89% from the previous week. At 4.2 million new cases, last week was 75% of the highest weekly total (April 2021). Europe continues to account for the vast majority of the increase, especially as the Omicron variant of concern (VOC) spreads throughout the region. The UK reported a record number of 78,610 new COVID-19 cases on December 15, 16% higher than its previous record set in January. Weekly incidence in Africa has more than doubled over last week, up from 79,491 new cases the week of November 29 to 167,682 new cases last week. Global weekly mortality has held relatively steady at approximately 50,000 deaths per week since late October.

Global Vaccination
The WHO reported 8.2 billion cumulative doses of SARS-CoV-2 vaccines administered globally as of December 13. A total of 4.35 billion individuals have received at least 1 dose, and 3.47 billion are fully vaccinated. Analysis from Our World in Data indicates that the overall trend in global daily vaccinations has increased since mid-October, up from 21.3 million doses per week to 36.4 million on December 15.* Our World in Data estimates that there are 4.45 billion vaccinated individuals worldwide (1+ dose; 56.55% of the global population) and 3.67 billion who are fully vaccinated (46.4% of the global population).
*The average daily doses administered may exhibit a sharp decrease for the most recent data, particularly over the weekend, which indicates effects of reporting delays. In an effort to reflect the longer-term trends, the numbers reported here may not correspond to the most recent data.

On December 13, the US surpassed 50 million cumulative COVID-19 cases:
1 case to 10 million: 289 days
10 to 20 million: 54 days
20 to 30 million: 85 days
30 to 40 million: 162 days
40 to 50 million: 100 days

As of December 14, the US CDC reports 50.2 million cumulative COVID-19 cases and 797,877 deaths. Daily incidence has increased steadily since the most recent low on October 24, up from 64,152 new cases per day to 117,950 on December 14—+84% over that period. Daily mortality is currently 1,143 deaths per day and likely will rise as daily incidence continues to increase.*

At the current pace, the US likely will surpass 800,000 cumulative deaths today or tomorrow. More people have died of COVID-19 in the US than are estimated to have died in the Civil War, the nation’s deadliest conflict (750,000 deaths). And the official number of COVID-19-related deaths likely is an undercount. If the US surpasses this benchmark on December 16:
1 death to 100k: 87 days
100k to 200k: 111 days
200k to 300k: 88 days
300k to 400k: 35 days
400k to 500k: 33 days
500k to 600k: 121 days
600k to 700k: 105 days
700k to 800k: 78 days

*Changes in state-level reporting may affect the accuracy of recently reported data, particularly over weekends. In an effort to reflect the longer-term trends, the numbers reported here may not correspond to the most recent dates.

US Vaccination
The US has administered 488.3 million cumulative doses of SARS-CoV-2 vaccines. Daily vaccinations have remained relatively steady over the past week, but have increased steadily since early July, up from 446,000 doses per day to 1.53 million on December 10, which is higher than the average prior to the Thanksgiving holiday weekend.*

There are 240 million individuals who have received at least 1 vaccine dose, equivalent to 72.3% of the entire US population. Among adults, 84.6% have received at least 1 dose, as well as 21.5 million children under the age of 18. A total of 202.8 million individuals are fully vaccinated**, which corresponds to 61.1% of the total population. Approximately 72.2% of adults are fully vaccinated, as well as 16.4 million children under the age of 18. Since August 13, 56.1 million fully vaccinated individuals have received an additional or booster dose, including 42.3% of fully vaccinated adults aged 65 years or older.
*Due to delays in reporting, estimates for the average daily doses administered are less accurate for the most recent 5 days. The most current average provided here corresponds to 5 days ago.
**Full original course of the vaccine, not including additional or booster doses.

IMMUNITY AGAINST OMICRON Preliminary results from laboratory studies examining the durability of immune responses following SARS-CoV-2 vaccines, and particularly booster doses, or previous SARS-CoV-2 infections in the face of the Omicron variant of concern (VOC) are coming fast and furious. While it is clear that the quickly spreading variant can cause breakthrough infections in fully vaccinated individuals and those who have recovered from previous infections, questions remain over how well the vaccines and their boosters will help prevent severe disease, hospitalization, or death.

The WHO held a global consultation on December 15 to examine evidence about Omicron’s ability to evade immunity, and heard reports on several studies suggesting that T cells—a type of white blood cell that play an important role in the human immune system—in vaccinated people can mount a robust defense against the VOC. While it seems increasingly likely that Omicron’s immune evasion will lead to an increase in new infections, even in fully vaccinated and previously infected individuals, researchers predict that T cells will maintain their ability to perform at a high level to help prevent severe disease. 

A preprint study—published on medRxiv and not yet peer-reviewed—from researchers working at Massachusetts General Hospital, Harvard University, and the Massachusetts Institute of Technology (MIT), reinforces the potential positive impact of booster doses. The research team explored how well the 3 vaccines authorized in the US (Moderna, Pfizer-BioNTech, and J&J-Janssen) withstood a pseudovirus that was built to imitate the Omicron VOC. The findings showed “low to absent” antibody neutralization from blood sera taken from people who received a complete regimen of vaccine. In positive results, individuals who had received booster doses of an mRNA vaccine exhibited potent neutralization of the Omicron pseudovirus, highlighting the potential importance of boosters in mounting stronger immune responses.

The idea of immune escape raises several questions about the future of currently available SARS-CoV-2 vaccines, with several schools of thought emerging. Some experts argue that individuals who have received full regimens of 2-dose SARS-CoV-2 vaccines will be sufficiently protected against severe outcomes of COVID-19, while others are pushing booster doses for fully vaccinated individuals based on several laboratory studies showing the extra dose might provide some additional protection. Other researchers are calling for a rapid investment into tailored vaccines specifically designed to address the Omicron variant. All 3 arguments have merits, and it remains unclear which direction the global community—at least those nations with sufficient vaccine access and capacity—will go. The conversation surrounding vaccine booster doses and SARS-CoV-2 variants will continue for the foreseeable future, changing as new data become available. 

BREAKTHROUGH CASES With the proportion of COVID-19 cases caused by the Omicron variant of concern (VOC) expected to surge in the coming weeks in the US, more data are being collected on who is becoming infected, including people who are fully vaccinated.* According to US CDC data published last week, 34 of the 43 Omicron cases initially recorded were in fully vaccinated people, 14 of whom had received a booster.** While much is still unknown about Omicron’s ability to dodge vaccine-induced immunity, it appears Omicron is able to skirt at least some protection garnered from vaccination and cause breakthrough cases. A new report from the Peterson-KFF Health System Tracker—which was conducted prior to Omicron’s detection and is based primarily on COVID-19 cases caused by the Delta variant—suggests that COVID-19 breakthrough cases are highly correlated with age (more common among those aged 65 and older) and underlying health conditions. A recent Wall Street Journal analysis came to the same conclusions. According to CDC data posted on November 22, unvaccinated persons had 14 times the risk of dying in September compared to vaccinated persons, showing that vaccination continues to be the best way to reduce the risk of severe disease, hospitalization, and death from COVID-19. 
*Full original course of the vaccine, not including additional or booster doses.
**Of those who had received a booster dose, 5 were within a 14-day window.

ASYMPTOMATIC CASES In a global meta-analysis published in JAMA Network Open, researchers from China found that 40.5% (95% CI, 33.50%-47.50%) of people who had confirmed positive tests for SARS-CoV-2 never became symptomatic. Although they represented only 0.25% (95% CI, 0.23%-0.27%) of the overall pooled tested population, the study highlights the potential transmission risk of asymptomatic cases in communities. The researchers included data from 95 individual studies covering 29,776,306 individuals undergoing testing. The pooled percentage of asymptomatic cases varied among different populations: 4.52% in nursing home residents or staff; 2.02% in air or cruise travelers; 2.34% in pregnant women; 1.46% in close contacts; 0.75% in healthcare workers or in-hospital patients; and 0.40% in community residents. Among confirmed cases, the pooled percentage of asymptomatic cases was notably highest among pregnant women (54.11%), followed by air or cruise travelers (52.91%), nursing home residents or staff (47.53%), community residents (39.74%), healthcare workers or in-hospital patients (30.01%), and close contacts (26.94%). In addition to the risk that an asymptomatic infected person could unwittingly pass the virus to others, infected asymptomatic individuals likely do not have robust immune responses and might not develop lasting neutralizing antibodies that could help ward off another infection. Additionally, people with asymptomatic COVID-19 still remain susceptible to post-acute sequelae of SARS-CoV-2 infection, or “long COVID.” The findings underline the importance of comprehensive, widespread testing and highlight the suspicion that many COVID-19 cases go undetected.

J&J-JANSSEN VACCINE CONTRAINDICATION ​​The US FDA on December 14 updated its fact sheets on the J&J-Janssen SARS-CoV-2 vaccine for healthcare providers and the general public to include a contraindication for individuals with a history of thrombosis with thrombocytopenia following the vaccine or any other adenovirus-vectored vaccine for COVID-19, as well as updated information about the risk of thrombosis with thrombocytopenia syndrome (TTS) following vaccination. The risk of TTS after vaccination using the J&J-Janssen vaccine remains low, but about 15% of cases have been fatal, according to the FDA. The highest reporting rate is among females between the ages of 30 and 49 (about 1 case per 100,000 doses administered). The US CDC’s Advisory Committee for Immunization Practices (ACIP) is meeting today to discuss the data and possibly recommend limitations on the use of the J&J-Janssen vaccine. The clotting issues also have been linked to the AstraZeneca-Oxford vaccine, which is not authorized in the US, but have not been reported with the mRNA vaccines from Moderna or Pfizer-BioNTech. 

VACCINE PASSPORTS Many nations, localities, and businesses are beginning to mandate proof of SARS-CoV-2 vaccination, or so-called vaccine passports, for entry onto public transportation and into venues such as restaurants, night clubs, and stadiums. Public health officials agree that vaccination is the best way to prevent COVID-19 or lower the risk of severe disease, but others question the utility of vaccine certificates, with some nations experiencing protests and riots. A modeling study published this week in The Lancet Public Health suggests that countries that required proof of vaccination, recent infection, or negative SARS-CoV-2 test to engage in activities or travel generally saw an increase in uptake of the vaccines. The researchers examined the effects of vaccine requirements in 6 countries and found that COVID-19 certifications lead to increased uptake of vaccines 20 days prior to implementation and up to 40 days following, with the highest increases among populations aged 49 and younger. More widespread vaccinations help to protect individuals from severe illness but also help curb the spread of SARS-CoV-2 in vulnerable communities and demographics, a critical issue amid the current Omicron variant of concern-associated surge. Policymakers should consider vaccine certification as part of their COVID-19 strategies to address vaccine complacency and hesitancy and potentially increase uptake but keep in mind ethical considerations, as the requirements will not work among all populations.

US COLLEGES & UNIVERSITIES The heightened transmissibility of the Omicron variant of concern (VOC) presents a number of new challenges for institutions that have returned to in-person or hybrid activities. US colleges and universities—which can be hotbeds for disease transmission given the frequency of large group gatherings and the existence of communal living spaces—are now revisiting their COVID-19 mitigation strategies to account for Omicron. Already, several schools have reported cases of the Omicron variant in addition to their weekly reports. Cornell University this week reported more than 900 new COVID-19 cases, with many suspected to be Omicron infections among fully vaccinated students, some of whom had received booster doses. Cornell decided to close in-person activity at its Ithaca branch in response to the outbreak. Other schools, including New York University, have begun to cancel nonessential gatherings and events and are requiring booster shots for students who plan to return to campus for the spring semester. While many colleges and universities are keeping their current mitigation strategies in place for the remainder of the fall semester, school officials are watching data closely to prepare for the larger challenge of what to do when students return in the new year.