16 August Episode 162: Importance of NPI for children and more on delta variant

Mon, 08/16/2021 - 16:37

Dear colleagues,


The present episode has two larger topics:

  • the importance of non-pharmacological interventions (NPI) in conjunction with vaccines, especially for school children;
  • an update on the delta variant related to various vaccines


Also papers on indications for third dose, pregnancy and cardiovascular complications are provided as well as some documents and websites of general interest.


Importance of NPI in the vaccine and delta era


Ep 162-1/2: A very interesting and well explained modeling on the consequences of school reopening.  These are the conclusions


The best place for children under 12 this fall is the classroom: universal masking and routine testing can ensure that they and their families remain safe and that their learning journey can continue smoothly

1.Kids under 12 years old are not yet eligible for vaccines and therefore remain unprotected

2.Without masks or testing, up to 90% of susceptible students may become infected by the end of the semester by the very infectious Delta (if only 30% have incoming protection)

3.Masks and testing, in combination, can prevent 40-70% of new infections


Consequences if not taken into account…

•Additional cases in the community--including among elderly grandparents and other family members--especially when community rates are already increasing.

•More infected students leads to more days of school absences, forcing caregivers to take time off work

•Multi-inflammatory syndrome or Long-Covid, which occurs among nearly half of students and can last up to 8 months


…and if school-based infections become too great, return to virtual learning

•Virtual learning is associated with…

–Prolonged mental health concerns among students

–Minimal or no learning gains

•Recall: the risk of severe disease for COVID-19 remains reduced for those of younger ages, in the event they do become infected within school


Ep 162-3: Another simulation exercise for the whole state of North Carolina (population 10.5 million, hence halfway between Sweden and Belgium) investigates the effect of vaccine coverage and efficacy combined or not with non-pharmacological interventions (NPI), including reduced mobility, school closings, and use of face masks.


In the scenario that is likely in Belgium: overall population vaccine coverage of 75 % with 90 % efficacy, they forecast without NPI over 527,000 new infections and only 450,000 with NPI by the end of the year.   


More news on DELTA


Ep 162-4: Detailed epidemiological analysis of Delta infections in Guandong:  very strict detection, follow up, trancing and quarantine amongst a total of 167 delta cases:

  • As a consequence of intervention, the Reproductive number dropped from 9 (25 May) to 0.5 (18 June) and then remained below 1 (Fig 2C p. 25)
  • The viral loads of Delta and wild type were rather similar at symptoms onset, but WT dropped much faster (Fig 3B p. 26): during first week Ct Delta was 23 versus 36 for wild type virus (which is many logs different in fact).  High viral loads were maintained between 4 days before onset of symptoms and 7 days after onset, then decreased gradually to a low but detectable level until about Day 20 (Figure 3A). As a consequence, the period that an infected person remains infectious is mainly between -4 and + 7 days.
  • Clearly, transmission of delta viruses occurred BEFORE symptoms onset in 73 % of the cases.  
  • Latent period (= time between infection and until PCR becomes positive) = only 4 days and incubation period (= time between infection and symptoms onset) = just less than 6 days.  
  • Viral load in (inactivated) vaccine breakthrough cases was 3 times lower.
  • The stepwise regression showed that a high infection risk was among those
    • in older age;  
    • exposed to an index case without or with 1 dose of vaccination
    • and being household and extended family contacts
  • 11.5 % of the infections resulted in severe disease, but no deaths.


Ep 162-5: Faster decline in viral load may explain why breakthrough infections with delta after mRNA vaccination result in much lower rates of severe disease , as compared to unvaccinated delta infections. See Fig 1 p. 16.

This can be explained by the high pre-existing antibody titers in vaccinated subjects that already partly neutralize delta and a presumed rapid boost by the infection itself expanding the effectiveness of the Ab against delta.

No distinction was made between Pfizer and Moderna.


Ep 162-6: Moderna protects about twice better against Delta infection than Pfizer: 86% protection by Moderna and 76% for Pfizer.  However, the protection against complicated disease, hospitalization, ICU and death was similarly high e.g. only 4-5 % of all breakthrough infections led to ICU admission and no deaths.

The reason for this difference is not known, but Moderna provides a higher RNA dose (200 µg) versus 60 for Pfizer.  The formulation and timing are also different.


CDC advice on third dose


Ep 162-7: Indications:

  • Blood cancers;
  • Active cancer treatment
  • Organ or stem cell transplant + immune suppressive treatment
  • Primary immune deficiency or untreated acquired immune deficiency (AIDS)
  • Immune suppressive treatment


COVID and pregnancy


Ep 162-8:  Review if 40 studies during COVID as compared to pre-pandemic:

  • More stillbirths (Odds 1.28): both in High and Low and Middle Income Countries
  • More maternal deaths (Odds 1.37): only in LMIC
  • More ruptured ectopic pregnancies (Odds 5.8) only in HIC
  • High rate of postnatal depression: both HIC and LMIC.


Remarkably: no difference for gestational diabetes, hypertension, pre-term delivery, low birth weight etc….


COVID as a trigger for acute cardiovascular event


Ep 162-9: A well-controlled nation-wide study in Sweden shows that COVID-19 provides a strong independent risk on first acute myocardial infarction as well as first ischemic stroke.  The RR is very high in the first week after infection (6-8 X higher); but remains elevated for several weeks.


See also the following interesting documents and websites:


Ep 162-10: An analysis of the COVAX initiative by the New York Times on 8th August


Ep 162-11: Extensive advice on the actions to be taken for the winter by the Academy of medical Sciences in London


Ep 162-12: A very elaborated advice on ventilation by the Belgian “High Council of Health” (in Dutch)  


Ep 162-13: Tracking the evolution of variants around the world



Ep 162-14: A nice overview on the COVID vaccine race by Reuters https://graphics.reuters.com/HEALTH-CORONAVIRUS/VACCINE-TRACKER/xegpbqnlovq/ 




  1. Several papers and advisory documents strongly advocate to maintain NPI, including masking, ventilation etc, during the Fall, especially in populations with low vaccination coverage, including children and particularly those under 12.  


  1. The infectiousness of the delta variant, even in vaccinated subjects, is being unraveled.  Moderna seems to protect better against breakthrough infection than Pfizer. Vaccination offers a robust protection against severe disease by Delta.


  1. The main complications of COVID in pregnancy are increased stillbirth and postnatal depression, observed around the world.  Increased maternal death is limited to low and middle income countries.  A striking increase in ruptured ectopic pregnancies has only been documented in high income countries.


  1. COVID strongly increases the risk on a first acute myocardial infarction of ischemic stroke.     


With many thanks for all the suggestions by our colleague Patrick Smits, Infectiologist at “Zorg en Gezondheid Vlaanderen”.


Best wishes,