Natural infection and / or vaccination? and Special report Mississippi
Delta in UK
Viral burden and vaccine effectiveness against new SARS-CoV-2 infections in the UK
Delta infections after two vaccine doses had similar peak levels of virus to those in unvaccinated people
Two doses of either vaccine, same level of protection against infection as natural infection
Natural infection followed by vaccination, even more protection than vaccination alone
After four to five months, effectiveness of these two vaccines similar
The time between doses does not affect effectiveness in preventing new infections
Now
Levels of immunity in the community
Implications for vaccination in children
Should we use virus or booster shots to top up immunity in adults?
Prof Eleanor Riley, immunologist, University of Edinburgh
We could be digging ourselves into a hole, for a very long time,
where we think we can only keep Covid away by boosting every year
Prof Adam Finn, government vaccine adviser
Over-vaccinating people when other parts of the world had none
a bit insane, it’s not just inequitable, it’s stupid
SARS-CoV-2 belongs to the β coronavirus family
Seventh known coronavirus to infect humans
Four cause colds, 229E, NL63, OC43, and HKU1
SARS-CoV, 2002
MERS-CoV, 2012
SARS-CoV-2, 2019
SARS-CoV-2
Single-stranded RNA-enveloped virus
Entire genome, 29,881 bases
Encoding 9,860 amino acids
28 proteins essential for infection
Breadth of immunity
How much of the virus the immune system learns to attack
Natural infection, more polyclonal
Moderna or Pfizer or Oxford-AstraZeneca, just spike protein
Keeps people out of hospital
28 proteins recognised give Lymphocytes a ‘target rich environment’
Prof Eleanor Riley, immunologist, University of Edinburgh
That means if you had a real humdinger of an infection, you may have better immunity to any new variants that pop up as you have immunity to more than just spike
Strength of immunity
Power to prevent infection and cause severe disease
In the case of breakthrough infection or reinfection
Asymptomatic, low levels of antibodies
Symptomatic or ill, higher levels of antibodies
Duration of immunity
Naturally enhanced neutralizing breadth against SARS-CoV-2 one year after infection
Natural infection, no vaccination
Antibody to the receptor binding domain, active
RBD-specific memory B cells, active and relatively stable between 6 and 12 months after infection
Vaccination further increases all components of the humoral response
Results in serum neutralizing activities against variants of concern
Similar to or greater than the neutralizing activity against the original Wuhan Hu-1 strain
achieved by vaccination of naive individuals
The data suggest that immunity in convalescent individuals will be very long lasting and that convalescent individuals who receive available mRNA vaccines will produce antibodies and memory B cells that should be protective against circulating SARS-CoV-2 variants.
Anatomical location of immunity
Immunoglobulin A, mucous membranes
Immunoglobulin M and G, in the blood
Prof Paul Klenerman, University of Oxford
The location of an infection makes a difference even if it’s the same virus,
so we would expect important differences between natural infection and vaccines
Current questions
Do vaccinated adults need to be boosted, or is exposure to the virus enough?
Do children need vaccinating at all, or does a lifetime of ongoing exposures build a good immune defence?
Immune top ups occur with respiratory syncytial virus, rhinoviruses, four other coronaviruses
Prof Adam Finn, government vaccine adviser
This isn’t proven, but it could be a lot cheaper and simpler to let that happen than spend the whole time immunising people
We could end up locked into a cycle of boosting without seeing if it was necessary
In children, argument had already been won
40-50% have already been infected and most weren’t ill or particularly ill
Prof Eleanor Riley, immunologist, University of Edinburgh
Using vaccines to take the edge off Covid,
followed by infection,
to broaden the immune response
We really need to consider, are we just frightening people rather than giving them the confidence to get on with their lives?
We’re close to just worrying people now.
