Africa sees significant jump in COVID-19 vaccination
Levels of COVID-19 vaccination in 31 African countries in the first 5 months of 2022 show a significant rise in COVID-19 immunization among high-risk groups, officials from the World Health Organization (WHO) African regional office said today at a briefing.
Nearly 50% of healthcare workers and people over age 60 have been fully vaccinated, up from 33% of health workers and 10% of people over 60 vaccinated by the end of 2021.
So far, two African countries—Mauritius and Seychelles—have met the 70% global target for overall population coverage, and Rwanda is expected to meet the target by the end of June. Nine countries have fully vaccinated 70% of the adult population, which is an emphasis in Africa, given that 45% of the population is in the lower-risk under-18 age-group.
Officials said 31 countries have mass vaccination campaigns scheduled for this year, and the WHO and its partners are focusing extra support for 14 countries that haven't yet vaccinated 10% of their populations.
Officials said Africa's COVID-19 cases were up slightly last week after a 3-week decline, mainly due to rises in East and North Africa.
Also, the WHO today welcomed a new licensing agreement between the Medicines Patent Pool and South Africa–based Biotech Africa to boost the supply and sale of COVID-19 serologic tests. WHO Director-General Tedros Adhanom Ghebreyesus, PhD, said in a statement that testing is the most effective way to get and keep ahead of the pandemic, adding that the agreement will leverage untapped manufacturing capacity to ensure easier access to affordable tests.
Jun 16 WHO African regional office press release
Jun 16 WHO statement
Boosters plus previous infection shown most protective against Omicron
According to a study yesterday based on COVID-19 cases in Qatar, protection afforded by natural immunity from prior infections was longer-lasting than from a primary mRNA vaccine series, but booster vaccine doses combined with prior infection provided the most protection against infections during the Omicron surge.
The study was published in the New England Journal of Medicine.
To conduct the study, researchers performed a national test-negative, case-control study in Qatar from Dec 23, 2021, through Feb 21, 2022, during the Omicron surge. They compared two doses of mRNA vaccines, three doses, natural immunity, and mixed immunity (from vaccines and natural infections).
Previous infection alone was 46.1% effective (95% confidence interval [CI], 39.5% to 51.9%) in protecting against infection with BA.2, an Omicron subvariant that surpassed the original (BA.1) Omicron strain in late March. Two doses of the Pfizer vaccine administered more than 6 months before the surge offered no protection (−1.1%; 95% CI, −7.1% to 4.6%), compared with three doses of Pfizer and no prior infection, which was 55.1% protective (95% CI, 50.9% to 58.9%).
The highest level of protection against BA.2 infection was in people who had a previous infection plus three doses of the Pfizer vaccine, which was 77.3% (95% CI, 72.4% to 81.4%).
Prior infections offered protection for up to 1 year, while a two-dose vaccine regimen offered little protection 6 months after the vaccine series was complete.
In addition, "previous infection alone, BNT162b2 [Pfizer] vaccination alone, and hybrid immunity all showed strong effectiveness (>70%) against severe, critical, or fatal Covid-19 due to BA.2 infection, " the authors wrote.
The authors concluded by saying the study shows the importance of vaccinating those with prior COVID-19 infections.
"Recent booster vaccination had moderate effectiveness, whereas hybrid immunity from previous infection and recent booster vaccination conferred the strongest protection against infection, at approximately 80%. All five forms of immunity were associated with strong and durable protection against Covid-19–related hospitalization and death," the concluded.
Jun 15 N Engl J Med study
Study finds low 2-dose vaccine protection against Omicron in teens
A study today in Pediatrics of Pfizer-BioNTech COVID vaccine efficacy (VE) in teens finds that VE was lower against symptomatic Omicron infection than against Delta and decreased faster, from 51% initially to 29% after 180 days, compared with 97% and 90% for the same intervals against symptomatic Delta infection.
Researchers in Toronto conducted a test-negative study among children aged 12 to 17 years who were tested for SARS-CoV-2 by polymerase chain reaction (PCR) from Nov 22, 2021 (when Omicron was first detected) to Mar 6, 2022. They restricted their Delta analysis to before Jan 3, 2022, because of the drop-off in Delta cases as Omicron surged.
The investigators compared 9,902 Omicron cases with 19,953 test-negative controls and 502 Delta cases with 17,930 controls. In their Omicron analyses, 91% of tested teens had received two doses and 1.3% had received three doses, with 84.5% having an interval between the first two doses of less than 8 weeks.
They estimated VE against symptomatic Omicron infection of 51% (95% confidence interval [CI], 38% to 61%) for 7 to 59 days after a second dose, but it dropped to 29% (95% CI, 17% to 38%) after 180 days, compared with 97% (95% CI, 94% to 99%) and 90% (95% CI, 79% to 95%) for Delta.
Overall, two-dose VE against severe Omicron outcomes was 85% (95% CI, 74% to 91%) 7 days or more after a second dose and held steady over time. (Numbers were too small for a similar Delta analysis.) Three-dose VE against symptomatic Omicron infection was 62% (95% CI, 49% to 72%).
The authors conclude, "These results can inform third dose recommendations in adolescents, as 2-dose protection against symptomatic Omicron infection is relatively low and wanes over time, whereas protection of a second dose against severe outcomes is higher."
Jun 16 Pediatrics abstract
CDC reports 16 more kids' unexplained hepatitis cases, 290 total
In a weekly update, the US Centers for Disease Control and Prevention (CDC) yesterday reported 16 more unexplained hepatitis cases in kids, raising the national total to 290 cases under investigation. So far, 41 states or jurisdictions have reported cases, up from 39 the previous week.
The CDC has said case increases don't necessarily signal a spike in new cases, given that investigations stretch back to October 2021.
Earlier this week the CDC said a study of background levels of unexplained hepatitis didn't show a spike over the COVID-19 pandemic months. Writing in Morbidity and Mortality Weekly Report (MMWR), the authors said their findings are based on limited data and come with a lot of caveats.
They also didn't see a change in adenovirus type 40/41 activity during the pandemic months. They said the findings can't confirm or rule out a link between hepatitis and adenovirus, but it said the analysis provides useful context for ongoing investigations.
Though a definitive cause hasn't been identified, experts have said adenovirus involvement is a strong lead, but they are also looking at other exposure, including SARS-CoV-2 and toxins.
As investigations continue, Israeli researchers recently published a case series detailing five children who recovered from COVID-19 and later experienced liver injury. Two were previously healthy young infants who needed liver transplants. Three were kids ages 8 to 13 with hepatitis who recovered after treatment with steroids. None had other infectious or metabolic causes.
Jun 15 CDC unexplained hepatitis update
Jun 14 CDC MMWR report
Jun 10 J Pediatr Gastroenterol Nutr study