AN ALTERNATIVE APPROACH: Are mix-and-match vaccines the way forward?

After discovering  that  especially  younger  women  who  received the shot faced an increased risk of danger-ous blood clots in the brain, however, Germany’s Standing  Committee  on  Vaccination  (Stiko)  in  April  recommended  limiting  use  of  AstraZeneca  to  people  over  60.

That  meant  quite  a  few  people  who  had  received  their  first  dose  of  AstraZeneca  had  to  then  get  BioNTech-Pfizer  or  Moderna  for  their  second  shot.  Today,  all  adults  in  Germany,  no matter their age, can be vaccinated with Astrazeneca again, if the patient and doctor have a conversation about the risks prior to the jab.But a new study shows that combining two different vaccines might be more valuable than just an  emergency  solution.

Researchers  at  Saarland  University  in  western  Germany  have  found  that  people   whose   first   shot   was   AstraZeneca   and   whose  second  shot  was  BioNTech-Pfizer  showed  an  immune  response  stronger  than  that  in  patients who had received two doses of the same vaccine.

Is it time to switch the world’s immunisation approach   to   a   mix-and-match   vaccination   for   everyone? Not quite yet.The findings coming out of Saarland University are preliminary and have not yet been fully evaluated  scientifically,  the  university  emphasised  in  the press statement sharing the results.

Before the researchers officially publish their findings, they will look into the role played by the age and gender of the patients, for example, and also delve deeper into  which  combinations  can  potentially  trigger  more severe side effects.Even though a full data evaluation hasn’t been completed yet, the team conducting the study was surprised  by  the  clear  results.

“That’s  why  we  wanted  to  share  our  outcomes  now  and  not  wait  for the scientific evaluation process to be completed,” Martina Sester, professor for transplantation- and infectional immunology at Saarland University, said in the press statement.There  were  250  people  that  participated  in  the  trial conducted at the University Hospital in Homburg, Saarland, over the last few months.

Some of them  received  two  AstraZeneca  shots,  some  received  two  BioNTech-Pfizer  shots  and  a  third  group  received  an  AstraZeneca  shot  followed  by  one  from  BioNTech.

The  researchers  compared  the  strength  of  participants’  immune  responses  two  weeks  after  the  second  shot.  “We  didn’t  just  look at the number of antibodies against the coronavirus [the participants] developed, but also how effective   the   so-called   neutralising   antibodies   were,”  Sester  explained.

“That  tells  us  how  good  the  antibodies  are  at  preventing  the  virus  from  entering our cells.”In  terms  of  antibody  development,  the  double-BioNTech as well as the combined AstraZeneca-BioNTech  vaccination  was  significantly  more  effective than the double-AstraZeneca alternative.

Participants who had one of the first two combinations of shots produced around 10 times more antibodies than those with two AstraZeneca jabs. And looking   at   the   neutralising   antibodies,   results   with  the  mix-and-match  vaccine  approach  were  “even  slightly  better”  than  those  achieved  with  two BioNTech shots, Sister said.

For vaccines that require  two  jabs,  health  officials  have  typically  recommended the second shot be the same as the first.  Since  there  were  no  changes  in  regulatory  recommendations   for   the   BioNTech   vaccine,   there  are  few  known  cases  of  people  receiving  a  BioNTech-Pfizer shot before an AstraZeneca shot.

The  Spanish  CombivacS  trial,  conducted  with  663  participants  at  the  Carlos  III  Health  Institute  in  Madrid,  came  to  a  similar  conclusion.  The  study’s  preliminary  results  were  reported  in  the  scientific  journal  Nature.  Like  the  results  from  Saarland  University,  they  are  not  yet  final,  the  publication  in  Nature  is  an  overview  of  what  the  researchers in Spain have found so far, and not a full,  peer-reviewed  article.

Two-thirds  of  participants received a shot of the BioNTech-Pfizer vaccine  after  their  initial  AstraZeneca  jab.  The  last  third  had  not  received  a  second  shot  at  the  time  the initial results were shared. Magdalena Camp-ins, an investigator on the CombivacS study at the Vall  d’Hebron  University  Hospital  in  Barcelona,  reported that those who had received the full mix-and-match vaccine combination began producing much  higher  levels  of  antibodies  after  their  second shot, and these antibodies were able to recognise   and   inactivate   SARS-CoV-2   in   laboratory   tests.

“It  appears  that  the  [BioNTech-]Pfizer  vaccine  boosted  antibody  responses  remarkably  in  one-dose  AstraZeneca  vaccines,”  said  Zhou  Xing,  an  immunologist  at  McMaster  University  in  Hamilton, Canada, who was not involved in the study, in the  Nature  article.  Xing  added  that  the  boost  appeared to be even more pronounced than the one in  people  who  had  received  their  second  dose  of  the AstraZeneca vaccine.

However, aside from the fact that its results aren’t yet finalised and peer-re-viewed, one problem with this study out of Spain is that it doesn’t include a control group of people who received two shots of the same vaccine — so no direct comparison between the two groups was possible.  Even  though  initial  results  are  promising,  the  World  Health  Organization  (WHO)  still  advises  against  combining  vaccines.

As  of  yet,  there is not sufficient data to assess whether this is a safe approach, says WHO spokeswoman Margaret  Harris.  In  Germany,  however,  someone  is  considered  fully  vaccinated  if  they  have  received  two  shots  of  the  same  vaccine,  as  well  as  if  they  have  had  a  mix-and-match  vaccination.  The  Ger-man  government  follows  the  guidelines  of  the  Paul Ehrlich Institute (PEI). That isn’t the case for all countries, though.

In Canada, for example, mix-and-match  vaccination  is  approved,  whereas  in  the US studies are still underway. And in the EU, it remains to be seen whether combined vaccines will be recognised by the digital vaccination pass, planned to come into effect in July. Vaccine combination ‘should be seriously considered If  the  initial  results  are  anything  to  go  by,  the  combination of AstraZeneca and BioNTech-Pfizer appears to be a promising way to immunise people against  COVID.  That’s  not  because  the  two  vaccines are in any way similar, though. They represent two types of COVID vaccines currently on the market. The AstraZeneca shot is a traditional vector vaccine.

It uses a harmless version of a different  virus  to  deliver  instructions  to  human  cells,  which  learn  to  build  up  antibodies  against  the  coronavirus. The BioNTech jab is an mRNA vaccine, a new kind of immunisation method. MRNA vaccines teach human cells how to make a protein that in turn triggers an immune response and the production of antibodies.Researchers don’t yet have enough information to  know  why  the  combination  of  these  two  vaccines  can  result  in  boosted  immunity.  Saarland  University  professor  Sester  said  she  was  looking  forward to seeing more research done on combining different types of vaccines and how they inter-act. “We believe that if other research teams reach conclusions  similar  to  ours,  the  combination  of  vector-  and  mRNA  vaccines  should  be  seriously  considered,” she said.