Sun, Mar 07, 2021 page6

• No chimps? Get AstraZeneca’s shot

  • By Hsieh Yen-yau 謝炎堯
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  The first batch of the AstraZeneca vaccine against COVID-19 has arrived in Taiwan, but many Taiwanese are more worried about the news than relieved.

  The concerns are born of news that many medical professionals in Europe inoculated with the AstraZeneca vaccine have fallen ill; that the vaccine is ineffective for those aged 65 or older; that the South African government has halted the vaccine’s rollout; and that Norway, Denmark, France, Germany, Italy and South Korea have temporarily suspended AstraZeneca inoculations of people aged 65 or older.

  It is important to clarify at the outset that the medical workers in Europe did not necessarily take time off for fever and headaches after being inoculated with the AstraZeneca vaccine.

  Also, Japan’s vaccination program, which began on Feb. 17 and uses the Pfizer-BioNTech vaccine, is being conducted in groups, based on the need to avoid staff shortages at hospitals and the belief that about one in seven of those vaccinated would need to take time off.

  The AstraZeneca, Russia’s Gamaleya Sputnik and the US’ Johnson & Johnson vaccines are all viral vector vaccines, which the US’ Operation Warp Speed program categorizes as type 2 vaccines.

  With type 2 vaccines, DNA material — with instructions to create the protein spikes that form on the surface of the novel coronavirus — is taken and modified before being placed inside a chimpanzee adenovirus-based vector that is unable to replicate itself.

  When the vaccine is injected into the human body it enters cells, carried on the adenovirus vector, and then goes about replicating the novel coronavirus’ protein spikes.

  These then induce the body’s immune system to produce neutralizing antibodies to fight the protein spikes, as well as stimulate the body’s T-lymphocytes to produce a tissue immune response, thereby creating a double immunity function.

  The Russian vaccine uses two human adenoviruses, reducing the chance of the efficacy of either dose being affected by adenovirus antibodies present in the body.

  For phase 3 clinical trials of the AstraZeneca vaccine, conducted in the UK, Brazil and South Africa, more than 23,000 adults were recruited, but only 9.7 percent were aged 65 or older.

  The participants in the South African trial possibly had antibodies for the chimpanzee adenovirus, which would have impeded the vaccine’s efficacy. The older the individual, the more likely that the antibodies were present and that more of them were present, affecting the ability of the vaccine to provide the intended protection.

  Their bodies would have produced antibodies against the chimpanzee adenovirus following the first dose, thereby impeding the efficacy of the second dose. As a result, halving the first dosage actually increased the protection it offered to 90 percent, and extending the intervening period before administering the second injection also led to more protection.

  In the Russian-produced vaccine, the first and second doses use different human-based adenovirus strains, so the protection offered is as high as 91.6 percent, while the single-dose Johnson & Johnson vaccine provides protection of 72 percent.

  The AstraZeneca vaccine obtained emergency approval from the WHO last month, making it the second vaccine to be accepted following the approval of the Pfizer-BioNTech jab.

  The WHO recommended that it be used for people aged 18 or older, and Australia has not restricted its use in the over-65 age group.

  South Korea started its national rollout of the AstraZeneca vaccine on Feb. 26. If Taiwan is to obtain the AstraZeneca vaccine produced by the company’s South Korean partner, SK Chemicals, then the Centers for Disease Control — emphatically not the Food and Drug Administration — should immediately dispatch a team of experts to inspect the plant to ensure that it complies with biosafety level 3 standards.

  The team should test the biosafety of the vaccine, obtain reports on adverse reactions to inoculations in South Korea and ensure that the information is readily available in Taiwan.

  Taiwanese can be inoculated using the AstraZeneca vaccine without undue concern, with two exceptions:

  First, those who have lived for extended periods in southern Africa, where chimpanzees are found, or those working in zoos, who could have had contact with chimpanzees and might have developed resistance to the vaccine.

  Second, the AstraZeneca vaccine contains low levels of alcohol, so those who experience anaphylactic shock from ingesting alcohol should not be given the vaccine.

  Hsieh Yen-yau is a retired professor of internal medicine at National Taiwan University’s College of Medicine.

  Translated by Paul Cooper
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